Development: How to add support for a device
First you should find, how your card identify yourself on pci (just lspci and lspci -vn). This give you type of main decoder chip and
Next, you should try to identify tuner chips that your card uses. There can be tuner chip, demodulator or both hidden in metallic box connected directly to antenna input. Often tuner type is printed under sticker.
You can find a lot of cards on http://bttv-gallery.de - very useful resource about cards identification.
Another useful place to look is windows drivers. They often contains a lot of information about cards hardware.
After that you should download latest v4l cvs and search for that or similar card. Probably something like your card is already supported but has another name. Otherwise, you can look on similar entries and fill entry for new card. For bttv chip you should correct bttv-cards.c and bttv.h, for cx88 - cx88-cards.c and cx88.h, for saa - saa7134-cards.c and saa7134.h
Card works - that's cool. You are ready to send patch to video4linux mailing list.