Well, technically speaking, there are no discrete USB controllers. All USB controllers are implemented within the PCH component (which happens to be the only component in the 100 Series chipsets).
The Q170 PCH contains a single xHCI USB controller. This controller can support up to 14 USB ports. Depending upon how many of the High-Speed I/O (HSIO) lanes are dedicated to USB 3.0 (as opposed to GbE, PCIe and SATA), up to 10 of these ports can be configured to support USB 3.0. These ports are exposed under a single USB 3.0 Root Hub.