RTEMS 4.6.1 On-Line Library

Console Driver Serial Driver Functioning Overview

BSP and Device Driver Development Guide

8.4: Serial Driver Functioning Overview

The following Figure shows how a Termios driven serial driver works:

Figure not included in this draft

The following list describes the basic flow.

the application programmer uses standard C library call (printf, scanf, read, write, etc.),
C library (in fact that's Cygnus Newlib) calls RTEMS system call interface. This code can be found in the c/src/lib/libc directory.
Glue code calls the serial driver entry routines.

BSP and Device Driver Development Guide