docs/devel: split qom-api reference into new file

Lets try and keep the overview of the sub-system digestible by
splitting the core API stuff into a separate file. As QOM and QDEV
work together we should also try and enumerate the qdev_ functions.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230630180423.558337-27-alex.bennee@linaro.org>

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

docs/devel/qdev-api.rst

+.. _qdev-api:
+
+================================
+QEMU Device (qdev) API Reference
+================================
+
+.. kernel-doc:: include/hw/qdev-core.h

docs/devel/qom-api.rst

+.. _qom-api:
+
+=====================================
+QEMU Object Model (QOM) API Reference
+=====================================
+
+This is the complete API documentation for :ref:`qom`.
+
+.. kernel-doc:: include/qom/object.h

docs/devel/qom.rst

@@ -387,4 +387,5 @@ OBJECT_DEFINE_ABSTRACT_TYPE() macro can be used instead:
 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.