Paul__B:
I think the point was that he wants to connect the (hardware) serial interface to the MIDI board, not the CP2102 USB interface, and was wondering whether this pin needed to be connected to anything.The answer is no - no need to to connect it to anything, just let it hang loose.
Yes, that's what I wanted! Thanks. Still wondering about RX/TX pins. I guess they just connect directly, after all it's microcontroller-to-microcontroller communication.