xawtv 4.x has DVB-T support in contrast to 3.x version available in portage and it is only DVB-T capable tv-viewer today AFAIK
I'm not keen on adding this to portage just yet. There are still only snapshots that are not said to be safe to work. I'm not sure if it's the only application supporting DVB-T, in general I think DVB is already quite well supported by other packages.
I am starting to look at getting a 4.x cvs snapshot working, but spotted this. There are apps which will do DVB already existing, kaffeine, mplayer, xine and so on. However it will be nice to have xawtv too. Sadly the development of the 4.x branch is not complete. If I get anything working I will post back, amybe with an ebuild if you are lucky ;-)
Oh, looks like i was beaten too it... http://bugs.gentoo.org/show_bug.cgi?id=135893