for PHS8 situaction is similar in please check description below. Additionally WWAN interface can also be used under Linux but since FW version 03001 arn0100107.  :

As a rule the CDC ACM Modem enumeration is compatible with generic CDC ACM based USB host drivers. However, to employ generic USB host drivers, specific issues may have to be taken into account depending on the operating system.

On a Linux system - e.g., Linux 2.6 Kernel with loadable module support and the USB host drivers "cdc_acm" as well as "usbserial" compiled as loadable modules - the "cdc_acm" driver enumerates the CDC ACM Modem port to /dev/ttyACMx. The "usbserial" driver enumerates its ports to /dev/ttyUSBx.

Depending on the AT^SDPORT settings, the above mentioned USB driver modules can be loaded to create the different ports. Please note that the command to load the modules may vary for different Linux distributions:

AT^SDPORT=6 (CDC ACM mixed mode with default delivery CDC ACM Modem enumeration) modprobe cdc-acm (only required if cdc-acm.ko is Kernel loadable module)

If PH8 is powered on, the following ports are created
/dev/ttyACM0: --> CDC ACM Modem Port
/dev/ttySx --> Application Port on ACS0

AT^SDPORT=3 (USB mode with Composite Communication Device enumeration) modprobe usbserial vendor=0x1E2D product=0x0053

if PH8 is powered on, following ports will be created
/dev/ttyUSB0 --> Reserved port (not usable)
/dev/ttyUSB1 --> NMEA port
/dev/ttyUSB2 --> Application port
/dev/ttyUSB3 --> Modem port
/dev/ttyUSB4 --> WWAN port (usable only  on newer FW than 03001 arn0100107 )

 AT^SDPORT=4 or 5 (Mixed modes with Composite Communication Device enumeration) modprobe usbserial vendor=0x1E2D product=0x0053

Creates the same ports as AT^SDPORT=3, but not all of them are accessible. With
AT^SDPORT=4 the application port is not accessible and only available over ASC0 through /dev/ttySx. With AT^SDPORT=5 the NMEA port is not accessible and only available over
ACS0 through /dev/ttySx. For more information on AT^SDPORT settings see [4] and [1].

To load the USB drivers automatically, a script realizing the above issues can be added to the other startup scripts - usually under etc/init.d - and the runlevels updated accordingly.

Regarding WWWAN usage - you configure PHS8 by AT command :

AT^SCFG="Serial/USB/DeviceClass/RmNet","CDC-ECM"
at+cgdcont=17,"IP","web.vodafone.de"
OK
at+cgact=1,17
OK

later  if necessary start DHCP by

root@DNT3202:/dev udhcpc -i eth2