As I say, not something I've played with either. However, as far as I know, you set up an IPTV stream using a pipe:// URL as per the following article:
https://tvheadend.org/projects/tvheadend/wiki/Custom_MPEG-TS_Input
... so the challenge becomes what command-line options you have to intercept the output from your camera and then translate it into a valid format. I agree that a basic how-to would be useful, but the real variable here is your camera, and that's something you'd need to work out for yourself (what formats it outputs, how, to where...).
I could be utterly wrong, though, or course :)