RS485 documentation: add 16C950 UART description
RS485 documentation: add 16C950 UART description

Add a notion about 16C950 UART, that is using DTR signal for RS485 mode.

Signed-off-by: Yegor Yefremov <379041fa42359f10443de1f461b1b247ec449fae@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@suse.de>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs