V4L/DVB (3809b): Added missing docs at kernel tree

Date:

From: Mauro Carvalho Chehab <mchehab@infradead.org>

There are some docs at V4L/DVB tree that were never included at kernel.
This patch includes those docs.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>