It is pretty straightforward to add you own custom board in platformio.
Please go through this link.
http://docs.platformio.org/en/latest/platforms/creating_board.html
Irrespective of the processor in question, the frameworks, upload_protocols are pretty much the same.
You can specify additional parameters like RAM/ROM, build flags and/or the VID/PID of the programmer/device.
I hope this helps you create you own custom board. 