Added SERIAL metadata into variant files.

Author: cmaglie

variants/yun/pins_arduino.h

@@ -25,3 +25,27 @@
 #include "../leonardo/pins_arduino.h"
 
 #define LED_BUILTIN 13
+
+// These serial port names are intended to allow libraries and architecture-neutral
+// sketches to automatically default to the correct port name for a particular type
+// of use.  For example, a GPS module would normally connect to SERIAL_PORT_HARDWARE_OPEN,
+// the first hardware serial port whose RX/TX pins are not dedicated to another use.
+//
+// SERIAL_PORT_MONITOR        Port which normally prints to the Arduino Serial Monitor
+//
+// SERIAL_PORT_USBVIRTUAL     Port which is USB virtual serial
+//
+// SERIAL_PORT_LINUXBRIDGE    Port which connects to a Linux system via Bridge library
+//
+// SERIAL_PORT_HARDWARE       Hardware serial port, physical RX & TX pins.
+//
+// SERIAL_PORT_HARDWARE_OPEN  Hardware serial ports which are open for use.  Their RX & TX
+//                            pins are NOT connected to anything by default.
+#define SERIAL_PORT_MONITOR        Serial
+#define SERIAL_PORT_USBVIRTUAL     Serial
+#define SERIAL_PORT_HARDWARE       Serial1
+#define SERIAL_PORT_LINUXBRIDGE    Serial1
+
+// this is defined in the Leonardo variant
+#undef  SERIAL_PORT_HARDWARE_OPEN
+