Update README.md

Co-authored-by: per1234 <[email protected]>

Author: facchinm

README.md

@@ -85,7 +85,7 @@ mkdir -p variants/$ALREADY_SUPPORTED_BOARD_NAME/{libs,conf}
 # ./mbed-os-to-arduino LPC546XX:LPC546XX
 ```
 
-This will produce almost all the files needed. To complete the port, add the board specifications to `boards.txt` (giving it an unique name) and provide `pins_arduino.h` and `variants.cpp` in `variants/$ALREADY_SUPPORTED_BOARD_NAME` folder.
+This will produce almost all the files needed. To complete the port, add the board specifications to [`boards.txt`](https://arduino.github.io/arduino-cli/latest/platform-specification/#boardstxt) (giving it a unique ID) and provide `pins_arduino.h` and `variants.cpp` in `variants/$ALREADY_SUPPORTED_BOARD_NAME` folder.
 Feel free to take inspirations from the existing variants :)
 
 For boards not supported by mainline `mbed-os`, the same applies but you should provide the path of your `mbed-os` fork