dmesg | less
That should take you to a block looking like this:
Serial driver version 5.05c (2001-07-08) with MANY_PORTS SHARE_IRQ SERIAL_PCI en
ttyS00 at 0x03f8 (irq = 4) is a 16550A
In my case the UART Chips is a 16550A with a 16Byte fifo, which should easily
cope with 115200 BAUD.