Updated documentation

Author: cmaglie

docs/platform-specification.md

@@ -1191,6 +1191,43 @@ If the **upload.protocol** property is not defined for a board, the Arduino IDE'
 behavior as ["Upload Using Programmer"](#upload-using-an-external-programmer). This is convenient for boards which only
 support uploading via programmer.
 
+### Overriding the default monitor port settings
+
+Each pluggable monitor has its own default settings that can be overridden using the following board properties:
+
+```
+BOARD_ID.monitor_port.PROTOCOL.SETTING_NAME=SETTING_VALUE
+```
+
+where:
+* `BOARD_ID` is the board identifier
+* `PROTOCOL` is the port protocol
+* `SETTING_NAME` and `SETTING_VALUE` are the port setting and the desired value
+
+For example, let's suppose that a board needs the `baudrate` setting of the `serial` port to be `9600`, then the corresponding properties in the `boards.txt` file will be:
+
+```
+myboard.monitor_port.serial.baudrate=9600
+```
+
+The setting name and value can be anything available in the [pluggable monitor settings](pluggable-monitor-specification.md#describe-command).
+
+#### Legacy `serial.disableRTS` and `serial.disableDTR` properties
+
+In the old Arduino IDE (<=1.8.x) we used the properties:
+
+```
+BOARD_ID.serial.disableRTS=true
+BOARD_ID.serial.disableDTR=true
+```
+
+to disable RTS and DTR when opening the serial monitor. The keep backward compatibilty the properties above are automatically converted to the corresponding pluggable monitor properties:
+
+```
+BOARD_ID.monitor_port.serial.rts=off
+BOARD_ID.monitor_port.serial.dtr=off
+```
+
 ### Serial port
 
 The full path (e.g., `/dev/ttyACM0`) of the port selected via the IDE or