AFAIK, most computers and notebooks have 2 USB controllers, because of the amount of power the USB devices can consume.
Which leads me to believe there lies your answer, because the amount of USB ports per controller is not going to help you (e.g. the max USB ports on 1 host is 127).
I guess you should try to find out the max power per USB port (based on the USB version standard), and reverse that to find out how much controllers there are.
USB 3 standard: 4.45V–5.25V (150 mA)
USB 1.1 & 2.0 : 4.75V-5.25V (100 mA)
So i guess, that by knowing the USB version of the port you can calculate how much controllers there are, based on Voltage and Ampere.