Tvheadend

I've modified the build that I'm running at home so that I can watch NTSC tv with tvheadend.
Although happy that I was able to get it to work with my setup it did take me a while because following someone else's logic isn't easy.

I recently bought an hdomerun prime with cable card support that works great with vlc but doesn't work all that great with tvheadend.
I've tried to use different permutations of dvbhdhomerun to get it to work but it just isn't right.

I would like to attempt to integrate libhdhomerun into tvheadend but I'm confused as to where I should start.

Is there a flow chart as to how the differnt parts interact with eachother? some sort of diagram? UML?