serial: 8250: move of_serial code to 8250 directory

As the of-serial driver is now 8250 specific, we can move the
file to a more appropriate place in teh 8250 subdirectory and
adapt the Kconfig help text and file name.

I'm leaving the CONFIG_SERIAL_OF_PLATFORM symbol unchanged
to avoid breaking user configuration files unnecessarily.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 25da430..54f8af8 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -377,3 +377,12 @@
 	  Selecting this option will enable handling of the extra features
 	  present on the UART found on Intel Medfield SOC and various other
 	  Intel platforms.
+
+config SERIAL_OF_PLATFORM
+	tristate "Devicetree based probing for 8250 ports"
+	depends on SERIAL_8250 && OF
+	help
+	  This option is used for all 8250 compatible serial ports that
+	  are probed through devicetree, including Open Firmware based
+	  PowerPC systems and embedded systems on architectures using the
+	  flattened device tree format.