Hi!
I don't think there is an explicit example for that but what you need is the serial-line.h. There is a method for initializing the driver in there and afterwards, all you need to do is let your process wait for a serial line event. On the PC side I used Java and the RXTX library. It was a bit tricky, because sometimes, the TTY line can be pretty unreliable and just randomly loose some of the data you send. If you want, I can post a basic example here. I also think that there is a serial line example in the contiki dist?
Greetz
Rainer