The system port driver always sends its own reset-bus requests directly to the miniport’s HwScsiResetBus routine, described in Section A.4.7.
However, it is possible for the HwScsiStartIo routine to be called with an SRB in which the Function member is set to SRB_FUNCTION_RESET_BUS if a Windows NT SCSI class driver requests this operation. The HwScsiStartIo routine can simply call the HwScsiResetBus routine to satisfy an incoming bus-reset request.