9 files changed, 108 insertions, 11 deletions
diff --git a/docs/devel/index-api.rst b/docs/devel/index-api.rst
index 7108821746..539ad29c21 100644
--- a/docs/devel/index-api.rst
+++ b/docs/devel/index-api.rst
@@ -11,5 +11,7 @@ generated from in-code annotations to function prototypes.
    loads-stores
    memory
    modules
+   qom-api
+   qdev-api
    ui
    zoned-storage
diff --git a/docs/devel/index-process.rst b/docs/devel/index-process.rst
index d50dd74c3e..362f97ee30 100644
--- a/docs/devel/index-process.rst
+++ b/docs/devel/index-process.rst
@@ -1,3 +1,5 @@
+.. _development_process:
+
 QEMU Community Processes
 ------------------------
 
diff --git a/docs/devel/index-tcg.rst b/docs/devel/index-tcg.rst
index b44ff8b5a4..a992844e5c 100644
--- a/docs/devel/index-tcg.rst
+++ b/docs/devel/index-tcg.rst
@@ -1,3 +1,5 @@
+.. _tcg:
+
 TCG Emulation
 -------------
 
diff --git a/docs/devel/index.rst b/docs/devel/index.rst
index 09cfb322be..abf60457c2 100644
--- a/docs/devel/index.rst
+++ b/docs/devel/index.rst
@@ -2,10 +2,30 @@
 Developer Information
 ---------------------
 
-This section of the manual documents various parts of the internals of QEMU.
-You only need to read it if you are interested in reading or
+This section of the manual documents various parts of the internals of
+QEMU. You only need to read it if you are interested in reading or
 modifying QEMU's source code.
 
+QEMU is a large and mature project with a number of complex subsystems
+that can be overwhelming to understand. The development documentation
+is not comprehensive but hopefully presents enough to get you started.
+If there are areas that are unclear please reach out either via the
+IRC channel or mailing list and hopefully we can improve the
+documentation for future developers.
+
+All developers will want to familiarise themselves with
+:ref:`development_process` and how the community interacts. Please pay
+particular attention to the :ref:`coding-style` and
+:ref:`submitting-a-patch` sections to avoid common pitfalls.
+
+If you wish to implement a new hardware model you will want to read
+through the :ref:`qom` documentation to understand how QEMU's object
+model works.
+
+Those wishing to enhance or add new CPU emulation capabilities will
+want to read our :ref:`tcg` documentation, especially the overview of
+the :ref:`tcg_internals`.
+
 .. toctree::
    :maxdepth: 1
 
diff --git a/docs/devel/qdev-api.rst b/docs/devel/qdev-api.rst
new file mode 100644
index 0000000000..3f35eea025
--- /dev/null
+++ b/docs/devel/qdev-api.rst
@@ -0,0 +1,7 @@
+.. _qdev-api:
+
+================================
+QEMU Device (qdev) API Reference
+================================
+
+.. kernel-doc:: include/hw/qdev-core.h
diff --git a/docs/devel/qom-api.rst b/docs/devel/qom-api.rst
new file mode 100644
index 0000000000..ed1f17e797
--- /dev/null
+++ b/docs/devel/qom-api.rst
@@ -0,0 +1,9 @@
+.. _qom-api:
+
+=====================================
+QEMU Object Model (QOM) API Reference
+=====================================
+
+This is the complete API documentation for :ref:`qom`.
+
+.. kernel-doc:: include/qom/object.h
diff --git a/docs/devel/qom.rst b/docs/devel/qom.rst
index c9237950d0..0b506426d7 100644
--- a/docs/devel/qom.rst
+++ b/docs/devel/qom.rst
@@ -13,6 +13,24 @@ features:
 - System for dynamically registering types
 - Support for single-inheritance of types
 - Multiple inheritance of stateless interfaces
+- Mapping internal members to publicly exposed properties
+
+The root object class is TYPE_OBJECT which provides for the basic
+object methods.
+
+The QOM tree
+============
+
+The QOM tree is a composition tree which represents all of the objects
+that make up a QEMU "machine". You can view this tree by running
+``info qom-tree`` in the :ref:`QEMU monitor`. It will contain both
+objects created by the machine itself as well those created due to
+user configuration.
+
+Creating a QOM class
+====================
+
+A simple minimal device implementation may look something like bellow:
 
 .. code-block:: c
    :caption: Creating a minimal type
@@ -26,7 +44,7 @@ features:
    typedef DeviceClass MyDeviceClass;
    typedef struct MyDevice
    {
-       DeviceState parent;
+       DeviceState parent_obj;
 
        int reg0, reg1, reg2;
    } MyDevice;
@@ -48,6 +66,12 @@ In the above example, we create a simple type that is described by #TypeInfo.
 #TypeInfo describes information about the type including what it inherits
 from, the instance and class size, and constructor/destructor hooks.
 
+The TYPE_DEVICE class is the parent class for all modern devices
+implemented in QEMU and adds some specific methods to handle QEMU
+device model. This includes managing the lifetime of devices from
+creation through to when they become visible to the guest and
+eventually unrealized.
+
 Alternatively several static types could be registered using helper macro
 DEFINE_TYPES()
 
@@ -98,7 +122,7 @@ when the object is needed.
    module_obj(TYPE_MY_DEVICE);
 
 Class Initialization
-====================
+--------------------
 
 Before an object is initialized, the class for the object must be
 initialized.  There is only one class object for all instance objects
@@ -147,7 +171,7 @@ will also have a wrapper function to call it easily:
 
    typedef struct MyDeviceClass
    {
-       DeviceClass parent;
+       DeviceClass parent_class;
 
        void (*frobnicate) (MyDevice *obj);
    } MyDeviceClass;
@@ -168,7 +192,7 @@ will also have a wrapper function to call it easily:
    }
 
 Interfaces
-==========
+----------
 
 Interfaces allow a limited form of multiple inheritance.  Instances are
 similar to normal types except for the fact that are only defined by
@@ -182,7 +206,7 @@ an argument to a method on its corresponding SomethingIfClass, or to
 dynamically cast it to an object that implements the interface.
 
 Methods
-=======
+-------
 
 A *method* is a function within the namespace scope of
 a class. It usually operates on the object instance by passing it as a
@@ -275,8 +299,8 @@ Alternatively, object_class_by_name() can be used to obtain the class and
 its non-overridden methods for a specific type. This would correspond to
 ``MyClass::method(...)`` in C++.
 
-The first example of such a QOM method was #CPUClass.reset,
-another example is #DeviceClass.realize.
+One example of such methods is ``DeviceClass.reset``. More examples
+can be found at :ref:`device-life-cycle`.
 
 Standard type declaration and definition macros
 ===============================================
@@ -382,9 +406,32 @@ OBJECT_DEFINE_ABSTRACT_TYPE() macro can be used instead:
    OBJECT_DEFINE_ABSTRACT_TYPE(MyDevice, my_device,
                                MY_DEVICE, DEVICE)
 
+.. _device-life-cycle:
+
+Device Life-cycle
+=================
+
+As class initialisation cannot fail devices have an two additional
+methods to handle the creation of dynamic devices. The ``realize``
+function is called with ``Error **`` pointer which should be set if
+the device cannot complete its setup. Otherwise on successful
+completion of the ``realize`` method the device object is added to the
+QOM tree and made visible to the guest.
+
+The reverse function is ``unrealize`` and should be were clean-up
+code lives to tidy up after the system is done with the device.
+
+All devices can be instantiated by C code, however only some can
+created dynamically via the command line or monitor.
 
+Likewise only some can be unplugged after creation and need an
+explicit ``unrealize`` implementation. This is determined by the
+``user_creatable`` variable in the root ``DeviceClass`` structure.
+Devices can only be unplugged if their ``parent_bus`` has a registered
+``HotplugHandler``.
 
 API Reference
--------------
+=============
 
-.. kernel-doc:: include/qom/object.h
+See the :ref:`QOM API<qom-api>` and :ref:`QDEV API<qdev-api>`
+documents for the complete API description.
diff --git a/docs/devel/tcg.rst b/docs/devel/tcg.rst
index b4096a17df..2786f2f679 100644
--- a/docs/devel/tcg.rst
+++ b/docs/devel/tcg.rst
@@ -1,3 +1,5 @@
+.. _tcg_internals:
+
 ====================
 Translator Internals
 ====================
diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index e85e26c4ca..fb651eae11 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -485,6 +485,12 @@ first to contribute the mapping to the ``libvirt-ci`` project:
    `CI <https://www.qemu.org/docs/master/devel/ci.html>`__ documentation
    page on how to trigger gitlab CI pipelines on your change.
 
+ * Please also trigger gitlab container generation pipelines on your change
+   for as many OS distros as practical to make sure that there are no
+   obvious breakages when adding the new pre-requisite. Please see
+   `CI <https://www.qemu.org/docs/master/devel/ci.html>`__ documentation
+   page on how to trigger gitlab CI pipelines on your change.
+
 For enterprise distros that default to old, end-of-life versions of the
 Python runtime, QEMU uses a separate set of mappings that work with more
 recent versions.  These can be found in ``tests/lcitool/mappings.yml``.