include/hw: document the device_class_set_parent_* fns

These are useful functions for when you want proper inheritance of
functionality across realize/unrealize calls.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230710153522.3469097-3-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/hw/qdev-core.h

@@ -952,9 +952,36 @@ void device_class_set_props(DeviceClass *dc, Property *props);
 void device_class_set_parent_reset(DeviceClass *dc,
                                    DeviceReset dev_reset,
                                    DeviceReset *parent_reset);
+
+/**
+ * device_class_set_parent_realize() - set up for chaining realize fns
+ * @dc: The device class
+ * @dev_realize: the device realize function
+ * @parent_realize: somewhere to save the parents realize function
+ *
+ * This is intended to be used when the new realize function will
+ * eventually call its parent realization function during creation.
+ * This requires storing the function call somewhere (usually in the
+ * instance structure) so you can eventually call
+ * dc->parent_realize(dev, errp)
+ */
 void device_class_set_parent_realize(DeviceClass *dc,
                                      DeviceRealize dev_realize,
                                      DeviceRealize *parent_realize);
+
+
+/**
+ * device_class_set_parent_unrealize() - set up for chaining unrealize fns
+ * @dc: The device class
+ * @dev_unrealize: the device realize function
+ * @parent_unrealize: somewhere to save the parents unrealize function
+ *
+ * This is intended to be used when the new unrealize function will
+ * eventually call its parent unrealization function during the
+ * unrealize phase. This requires storing the function call somewhere
+ * (usually in the instance structure) so you can eventually call
+ * dc->parent_unrealize(dev);
+ */
 void device_class_set_parent_unrealize(DeviceClass *dc,
                                        DeviceUnrealize dev_unrealize,
                                        DeviceUnrealize *parent_unrealize);