Export Leonardo second serial port as a tty on Linux and COM under windows


I would like to be able to use the second serial port of the Leonardo (pin 0 & 1) through USB.

Is there an easy solution to export this port to my OS as a COM port on Windows and a ttyUSB on linux. (There is already one exported for the bootloader and communications through Serial.*)

More generally, where is the good place to code usb capability extensions for the Leonardo (Ideally available from sketches).

I think it's in hardware/arduino/cores/arduino/USBAPI.h

I'm new to Arduino, but I'm experienced in bare mcu programming.