I have an LG Smart 3D TV, it connects to my LG BluRay player via its SimpleLink functionality. When I plugged the Pi into the System it picks it up as a DVR device in the simple link menu ... LG FTW! So From the simplelink I select the DVR, which puts me onto the Pi input on my HDMI 2. I'm not 100% sure but I think its communicating either via the HDMI or else the Wired network...
FYI, I figured this out purely accidentally, I bumped my LG TV remote the other night and the movie nav buttons popped up, prior to that I was using Yatse on my phone..
EDIT: Ahh .. found this page about
CEC... explains it