The TCON always comes from the panel maker (except in rare cases where It's outsourced due to cost or panel maker limitations, in budget TVs). In a very simplistic way to explain it, it's an intrinsic part of the panel, it interprets the video signal from the processor for the panel to display video.
Panasonic usually just buy their picture processing in from a SOC manufacturer for every model apart from the FX750, the HCX processor and just "tune" the off the shelf SOC to their liking, much like every budget manufacturer (eg Hisense).