The chip is likely to be an OEM custom part with no datasheet and no market availability. Whoever commissioned the chip has probably consumed all the pieces that have ever been made or ever will be made.
I guess you guys are right, these lights speak fluent Chinese, and they are so cheap on flea-bay I suspect they've sold thousands of them, and are still selling them by the thousand ... the silkscreen on the board says 2017-03-08, so they've already had more than 3 years production run ...
I've got to rethink how I'm going to use the control board now, I will probably have to use it "as is" and interface the MOSFET drivers (low-side) to my existing Arduino driving some under-seat RGB LED lighting.