View serial ports/multi-port boards (must be root)

setserial /dev/ttyS0
setserial /dev/ttyS1

Set a serial port to 115k (must be root)

setserial /dev/ttyS0 spd_vhi
This only configures the port, not any attached modem or serial device.
Other speeds:
spd_normal 38.4 k
spd_hi 57.6k
spd_shi 230k
spd_warp 460k