This follows the pattern of other peripherals (I2C, SPI) to specify the pins using pin objects instead of a pair of GPIO port and pin number. It makes it easier to customise the UART pins for a particular board.
- Put the I2C bus on the corect pins - Add the appropriate board_init to power the shield
This compiles and links, but hasn't been tested on a board yet and even if it was run, it doesn't currently do anything.