UART 16550

Several pages on opencores, including:

• https://opencores.org/projects/uart16550 which has wishbone
• https://github.com/freecores/uart16550 freecores version (basically same as above)
• https://git.m-labs.hk/M-Labs/HeavyX/src/branch/master/heavycomps/heavycomps/uart.py
• https://github.com/antonblanchard/lpcperipheral/blob/master/lpcperipheral/lpcfront.py