[media] v4l2-framework: update documentation

'parent' was renamed to 'dev_parent'. Clarify how/when this should be used.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/v4l2-framework.txt

@@ -574,9 +574,13 @@ of the video device exits.
 The default video_device_release() callback just calls kfree to free the
 allocated memory.
 
+There is also a video_device_release_empty() function that does nothing
+(is empty) and can be used if the struct is embedded and there is nothing
+to do when it is released.
+
 You should also set these fields:
 
-- v4l2_dev: set to the v4l2_device parent device.
+- v4l2_dev: must be set to the v4l2_device parent device.
 
 - name: set to something descriptive and unique.
 
@@ -613,15 +617,16 @@ You should also set these fields:
   If you want to have a separate priority state per (group of) device node(s),
   then you can point it to your own struct v4l2_prio_state.
 
-- parent: you only set this if v4l2_device was registered with NULL as
+- dev_parent: you only set this if v4l2_device was registered with NULL as
   the parent device struct. This only happens in cases where one hardware
   device has multiple PCI devices that all share the same v4l2_device core.
 
   The cx88 driver is an example of this: one core v4l2_device struct, but
-  it is used by both an raw video PCI device (cx8800) and a MPEG PCI device
-  (cx8802). Since the v4l2_device cannot be associated with a particular
-  PCI device it is setup without a parent device. But when the struct
-  video_device is setup you do know which parent PCI device to use.
+  it is used by both a raw video PCI device (cx8800) and a MPEG PCI device
+  (cx8802). Since the v4l2_device cannot be associated with two PCI devices
+  at the same time it is setup without a parent device. But when the struct
+  video_device is initialized you *do* know which parent PCI device to use and
+  so you set dev_device to the correct PCI device.
 
 - flags: optional. Set to V4L2_FL_USE_FH_PRIO if you want to let the framework
   handle the VIDIOC_G/S_PRIORITY ioctls. This requires that you use struct