Man page 9 : subsys_virtual_register

subsys_virtual_register - register a subsystem at /sys/devices/virtual/

int subsys_virtual_register(struct bus_type *  subsys , const struct attribute_group **  groups );

subsys
    virtual subsystem

groups
    default attributes for the root device

All AqvirtualAq subsystems have a /sys/devices/system/<name> root device with the name of the subystem. The root device can carry subsystem-wide attributes. All registered devices are below this single root device. ThereAqs no restriction on device naming. This is for kernel software constructs which need sysfs interface.