video4linux

While I've been making this kernel in gentoo the lessons I've learnt are valid throughout.
I have a Tevion DVBT-220RF card. Support for this in linux has been available since March 06.
To find what I needed I had to get to the video4linux developer mailing list archives. They aren't indexed by google. http://marc.theaimsgroup.com/?l=linux-video
Use the search feature to find subjects which match your tv card description.
From here you find out if you really need a new patch to run your card.
V4l offers mercurial to build these patches for you.
While the wiki http://linuxtv.org/v4lwiki/index.php/How_to_build_from_mercurial
says a kernel newer than 2.6.10 is needed, that's out-of-date and a newer kernel again was required. I went to 2.6.16, with patches, hoping to have the tv card going, but still had to use mercurial to get the latest patches for the tv cards.
the wiki doesn't tell you to start from /usr/src/linux, but it can't find your kernel headers otherwise.
Summary:
New kernel;
Install at least kernel headers;
Get mercurial (apt-get);
Cd /usr/src/linux;
follow instructions from v4lwiki.