Add submodule dependency filesHEADmaster

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+The support for multiple serial interfaces as implemented is mainly
+intended to allow for modem dial-in / dial-out while still being able
+to use a serial console on a (different) serial port.
+
+MPC8XX Specific
+===============
+At the moment, the ports must be split on a SMC and a SCC port  on  a
+8xx processor; other configurations are not (yet) supported.
+
+Support for hardware handshake has not been implemented yet (but is
+in the works).
+
+*) The default console depends on the keys pressed:
+	- SMC if keys not pressed (modem not enabled)
+	- SCC if keys pressed (modem enabled)
+
+*) The console can be switched to SCC by any of the following commands:
+
+	setenv stdout serial_scc
+	setenv stdin serial_scc
+	setenv stderr serial_scc
+
+*) The console can be switched to SMC by any of the following commands:
+
+	setenv stdout serial_smc
+	setenv stdin serial_smc
+	setenv stderr serial_smc
+
+*) If a file descriptor is set to "serial" then the current serial device
+will be used which, in turn, can be switched by above commands.
+
+*) The baudrate is the same for all serial devices. But it can be switched
+just after switching the console:
+
+	setenv sout serial_scc; setenv baudrate 38400
+
+After that press 'enter' at the SCC console. Note that baudrates <38400
+are not allowed on LWMON with watchdog enabled (see CONFIG_SYS_BAUDRATE_TABLE in
+include/configs/lwmon.h).
+
+
+PPC4XX Specific
+===============
+*) The default console is UART0
+
+*) The console can be switched to UART1 by any of the following commands:
+	setenv stdout serial1
+	setenv stderr serial1
+	setenv stdin serial1
+
+*) The console can be switched to UART0 by any of the following commands:
+	setenv stdout serial0
+	setenv stderr serial0
+	setenv stdin serial0