UART driver: read function

[Sebastian Huber]

----- Daniel Krüger <daniel.krueger at systec-electronic.com> schrieb:
> Beside some problems/differences between newlibc and glibc, one 
> RTEMS-specific questions remains unanswered:
> 
> What is the right implementation for the UART driver read function 
> (console_fns.deviceRead)? It seems to be implemented differently from 
> target to target. Some implementations return -1 if the receive FIFO is 
> empty and some implementations do a busy waiting for new characters.

The new Termios device API is documented here:

https://docs.rtems.org/doc-current/share/rtems/html/bsp_howto/Console-Driver.html#Console-Driver

A busy wait in the polled read handler is a driver bug.