The ATSC M/H specific properties are not properly documented.
This became crearer when converting the existing data into
tables and adding cross references.

For now, just add placeholders, as a further investigation
about the meaning of each parameter is required.

Cc: Michael Ira Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>