[VirtIO] README: add serial-related run_arduino.sh commands

Author: kbumsik

variants/STM32MP157_DK/README.md

@@ -33,7 +33,9 @@ Note: `sh run_arduino.sh start` is a one-shot command: the Arduino firmware only
 
 `run_arduino.sh` help page summary:
 
-    Usage: sh run_arduino.sh [start|stop|restart|generate|install|uninstall]
+    Usage: sh run_arduino.sh [start|stop|restart]
+           sh run_arduino.sh [install|uninstall]
+           sh run_arduino.sh [monitor|send-msg|send-file|minicom]
 
     run_arduino.sh is a helper script that helps managing an Arduino binary
     file for the coprocessor using remoteproc framework.
@@ -49,6 +51,18 @@ Note: `sh run_arduino.sh start` is a one-shot command: the Arduino firmware only
     sh run_arduino.sh uninstall
         Uninstall the autostart service.
 
+    sh run_arduino.sh monitor
+        Monitor data received from the coprocessor via the virtual serial.
+
+    sh run_arduino.sh send-msg <message...>
+        Send a message to the coprocessor via the virtual serial.
+
+    sh run_arduino.sh send-file <filename>
+        Send a file content to the coprocessor via the virtual serial.
+
+    sh run_arduino.sh minicom
+        Launch minicom interactive serial communication program.
+
     sh run_arduino.sh stop
         Stop the coprocessor.