Add SDR specific notes to G_MODULATOR / S_MODULATOR documentation.
Signed-off-by: NAntti Palosaari <crope@iki.fi>
[hans.verkuil@cisco.com: add quotes in "The term 'modulator'"]
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>