Apple - What is iBridge

The iBridge is the USB link to the Touch Bar. It is noted in http://arstechnica.com/video/2016/11/the-2016-13-and-15-inch-touch-bar-macbook-pros-reviewed/ in the "Inner workings..." section.

iBridge is the code name for the T series coprocessor (e.g. T1 or T2 chip) in newer Macs. It manages the Touch ID sensor, as well as the FaceTime camera and audio control. It is present even on Macs that don't have a Touch Bar, like the 2018 MacBook Air and Mac mini.