fix(uart_doc): Document RX and TX pin detachment behavior

Added note about driver behavior when RX and TX pins are detached.

Author: SuGlider

docs/en/api/serial.rst

@@ -23,6 +23,10 @@ with additional features for advanced use cases.
 * **Event callbacks**: Receive and error event callbacks
 * **Configurable buffers**: Adjustable RX and TX buffer sizes
 
+.. note::
+   In case that both pins RX and TX are detached from UART, the driver will be stopped.
+   Detaching may occur when, for instance, starting another peripheral using RX and TX pins, such as Wire.begin(RX0, TX0).
+
 UART Availability
 -----------------