[PATCH 18/18] Documentation: media: Document sub-device notifiers

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Document that sub-device notifiers are now registered using
v4l2_async_subdev_nf_init(). No documentation is changed as it seems that
sub-device notifiers were not documented apart from kernel-doc comments.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 Documentation/driver-api/media/v4l2-subdev.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
index 1c5cb1a637ab..b034c35000f8 100644
--- a/Documentation/driver-api/media/v4l2-subdev.rst
+++ b/Documentation/driver-api/media/v4l2-subdev.rst
@@ -204,6 +204,12 @@ that the bridge device needs for its operation. Several functions are available
 to add subdevice descriptors to a notifier, depending on the type of device and
 the needs of the driver.
 
+For a sub-device driver to register a notifier, the process is otherwise similar
+to that of a bridge driver, apart from that the notifier is initialised using
+:c:func:`v4l2_async_subdev_nf_init` instead. A sub-device notifier may complete
+only after the V4L2 device becomes available, i.e. there's a path via async
+sub-devices and notifiers to that root notifier.
+
 :c:func:`v4l2_async_nf_add_fwnode_remote` and
 :c:func:`v4l2_async_nf_add_i2c` are for bridge and ISP drivers for
 registering their async sub-devices with the notifier.
-- 
2.30.2