Have Cell Phone Display Panel(s) been hacked to accept HDMI?
Interfacing to random LCD panels is still in the "Wild West" phase. It may take a lot of hacking and going through solutions that won't work.  There are US$20 boards from China that claim to be able to interface to a variety of raw LCD panels. They come with all the "TV receiver" functionality including an off-air TV tuner and HDMI input and even composite and RGB (or component) input.  It is pretty much a gamble whether any of them will work for any particular display panel and it's not even a good bet at this point in history (May, 2016). Good luck.