There was a topic on the forum regarding digital tuners on BSD, but I was sorta opposed of the idea.. was FreeBSD specific.
http://www.daemonforums.org/showthread.php?t=1411
I'm sure I've seen a few 3rd party projects related to developing drivers for specific devices, the problem is.. there are many devices, all with unique and incompatible designs.
The OpenBSD project wrote a V4L layer video(4), and a uvideo(4) driver exists for UVC web cams.. but, at the moment.. all that exists for tuners is the driver for Brooktree chipsets
bktr(4) (
All Analog AFAIK).