docs/library/machine.UART.rst: Specify optional txbuf and rxbuf args.
If a port would like to expose the configuration of transmit and/or receive
buffers then it can use these arguments.
@@ -56,6 +56,8 @@ Methods
- *tx* specifies the TX pin to use.
- *rx* specifies the RX pin to use.
+ - *txbuf* specifies the length in characters of the TX buffer.
+ - *rxbuf* specifies the length in characters of the RX buffer.
On the WiPy only the following keyword-only parameter is supported:
