Local device notifications. Is called if list of local devices changed (device was plugged into
a USB port/unplugged)




devname - sys name of device (unique USB device identifier obtained from
kernel: hub-port[.port ...])
maxchild - number of hub ports (= 0 for USB devices, > 0 for hubs)
name - device name
added - true if device was connected to a USB port, false if it was disconnected