Virtual bus driver as a "system device"

Hello,

We have a virtual bus driver that have multiple virtual LAN devices on it.
I have asked WHQLNet and they said that they have no program to test the
virtual bus driver. However, the bus driver can be submitted to the NDIS
Window Logo program with the NDIS driver of its child devices. The virtual
bus driver will be logo'd and digitally signed if the NDIS drivers pass
certification.

A question that they could not answer is if the virtual bus driver instances
can be listed in the "System devices" sub-tree in the Windows Device
Manager. This effectively makes the virtual bus driver instances as devices
of the system class.

I would like to know the criteria that justify a device as a "system" device
and being listed in the "System devices" sub-tree in the Windows Device
Manager.

Thank you very much for your help.
--Hieu