V4L/DVB: V4L: File handles: Add documentation
V4L/DVB: V4L: File handles: Add documentation

Add documentation on using V4L2 file handles (v4l2_fh) in V4L2 drivers.

Signed-off-by: Sakari Ailus <8d98c2be02a446df653daa2c00496b87f3f016e4@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <ad86ba2154032c9f55743a190faa2459a9d61d42@redhat.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs