NXP also makes SPI/I2C UARTs.
Example of a dual UART:
sc16is752
Skyjumper used this on a project a while ago, I am doing up code for another project now.
Have to change the crystal before I test. Blindly copied crystal from '2560 and didn't change the frequency from 16 MHZ to 11.0592 MHZ.
16 MHz can't be divided by anything to get 115,200, while 11.0592 /96 = 115200