Tool/software:
Cascading USB hubs means to connect a root USB hub to the next tier which has another one or more hubs and few other devices and carrying forth in multiple tiers of hubs and devices. The USB standard specifies the maximum tier topology of 7 tiers (5 for HUBs,1 for Host, and 1 for Device)
For Hub cascading design, recommend to use up layer Vbus to control USB_VBUS of lower layer hub
