net/usb: Ethernet quirks for the LG-VL600 4G modem

This adds a driver for the CDC Ethernet part of this modem.  The
device's ID is blacklisted in cdc_ether.c and is white-listed in
this new driver because of the quirks needed to make it useful.
The modem's firmware exposes a CDC ACM port for modem control and a
CDC Ethernet port for network data.  The descriptors look fine but
both ports actually are some sort of multiplexers requiring non-
standard headers added/removed from every packet or they get
ignored.  All information is based on a usb traffic log from a
Windows machine.

On the Verizon 4G network I've seen speeds up to 1.1MB/s so far with
this driver, a speed-o-meter site reports 16.2Mbps/10.5Mbps.
Userspace scripts are required to talk to the CDC ACM port.

Signed-off-by: Andrzej Zaborowski <balrogg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/Kconfig

@@ -433,4 +433,19 @@ config USB_SIERRA_NET
 	  To compile this driver as a module, choose M here: the
 	  module will be called sierra_net.
 
+config USB_VL600
+	tristate "LG VL600 modem dongle"
+	depends on USB_NET_CDCETHER
+	select USB_ACM
+	help
+	  Select this if you want to use an LG Electronics 4G/LTE usb modem
+	  called VL600.  This driver only handles the ethernet
+	  interface exposed by the modem firmware.  To establish a connection
+	  you will first need a userspace program that sends the right
+	  command to the modem through its CDC ACM port, and most
+	  likely also a DHCP client.  See this thread about using the
+	  4G modem from Verizon:
+
+	  http://ubuntuforums.org/showpost.php?p=10589647&postcount=17
+
 endmenu