This implements basic support for all 843x RS232 devices, but does not
add DMA support.  This means that sustained data transfers at high baud
rates may not be possible on multiple ports simultaneously.
Signed-off-by: NShawn Bohrer <shawn.bohrer@ni.com>
Signed-off-by: NAlan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>