Device uses an LG L2000 LTE chip and a Qualcomm MDM6800A for CDMA/EVDO.

The firmware flasher tool speaks DIAG and includes a lot of LTE-related
NV items.

Device has two USB interfaces:

0 - Proprietary ethernet interface
1 - CDC-ACM serial port

The ACM port speaks a proprietary protocol that MUX-es traffic from the
following virtual interfaces (according to Windows):

0: LGE LTE DM Port
1: LGE USB Modem Port
2: LGE LTE RF Serial Port (com)
3: LGE CDMA USB Serial Port (com)
4: LGE CDMA USB GPS NMEA Port (com)
5: LGE CDMA LBS Serial Port (com)

MUX Header Format
-----------------

u32: magic, always [ 0x5a 0x48 0x12 0xa5 ]
u32: sequence number (unpaired; host and device use separate sequence numbers)
u32: length (not including this header, but including any padding)
u16: MUX channel (21 f0: CMD) (11 f0: AT)
<data>


Packets are 4-byte aligned with padding of zeros, and this padding is included
in the length given in the header.

AT commands may have trailing junk bytes.  It appears that interpreters should
simply ignore any data in AT packets after the last CRLF.

CMD packets are terminated with a standard HDLC CRC-16 and 0x7E.

