[POWERPC] Open Firmware serial port driver

This can be used for serial ports that are connected to an
OF platform bus but are not autodetected by the lecacy
serial support.
It will automatically take over devices that come from the
legacy serial detection, which usually is only one device.

In some cases, rtas may be set up to use the serial port
in the firmware, which allows easier debugging before probing
the serial ports. In this case, the "used-by-rtas" property
must be set by the firmware. This patch also adds code to the
legacy serial driver to check for this.

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 5cc6b91..d0edbaa 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -999,4 +999,14 @@
 	  If you have enabled the serial port on the Motorola IMX
 	  CPU you can make it the console by answering Y to this option.
 
+config SERIAL_OF_PLATFORM
+	tristate "Serial port on Open Firmware platform bus"
+	depends on PPC_OF
+	depends on SERIAL_8250
+	help
+	  If you have a PowerPC based system that has serial ports
+	  on a platform specific bus, you should enable this option.
+	  Currently, only 8250 compatible ports are supported, but
+	  others can easily be added.
+
 endmenu