BPI-M2 Ultra UART port

UART specification:

The header CON4 is the UART interface. For developers of Banana Pi, this is an easy way to get the UART console output to check the system status and log message.

CON2 Pin Name	Default Function	GPIO
CON2 P03	UART0-TXD
CON2 P02	UART0-RXD
CON2 P01	GND