USB: add usb-serial spcp8x5 driver

Original version of the driver done by Linxb, changes by Harald, and
lots of cleanups by me in order to get it into a mergable state.

Cc: Linxb <xubin.lin@worldplus.com.cn>
Cc: Harald Klein <hari@vt100.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
index a769f6a..f9c6c09 100644
--- a/drivers/usb/serial/Kconfig
+++ b/drivers/usb/serial/Kconfig
@@ -503,6 +503,16 @@
 	  To compile this driver as a module, choose M here: the
 	  module will be called oti6858.
 
+config USB_SERIAL_SPCP8X5
+	tristate "USB SPCP8x5 USB To Serial Driver"
+	depends on USB_SERIAL
+	help
+	  Say Y here if you want to use the spcp8x5 converter chip.  This is
+	  commonly found in some Z-Wave USB devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called spcp8x5.
+
 config USB_SERIAL_HP4X
         tristate "USB HP4x Calculators support"
         depends on USB_SERIAL