Merge PR arduino#514 "Add note re: irrelevance of Serial.begin() for USB CDC ports" from per1234

Add note re: irrelevance of Serial.begin() for USB CDC ports

Author: robsoncouto

Language/Functions/Communication/Serial/begin.adoc

@@ -112,5 +112,11 @@ void loop() {}
 [%hardbreaks]
 Thanks to Jeff Gray for the mega example
 
+
+[float]
+=== Notes and Warnings
+For USB CDC serial ports (e.g. `Serial` on the Leonardo), `Serial.begin()` is irrelevant. You can use any baud rate and configuration for serial communication with these ports. See the list of available serial ports for each board on the link:../../serial[Serial main page].
+[%hardbreaks]
+
 --
 // HOW TO USE SECTION ENDS