What is LPSS Serial Adapter in my network tab
The LPSS adapters are related to a chip feature on the new 2016 MacBook Pros.  I found these interfaces present immediately after setting up a new 15-inch 2016 Touch Bar model out of the box (before plugging in any peripherals or installing any drivers).

The following patent filing for the "low power subsystem" describes an interface through which a "secondary" processor can provide access to the system's memory while the primary processor is powered down:


  The subsystem acts independently of the CPU, which would not be able to perform the necessary functions during low power mode. The subsystem allows the notebook to perform several functions while in the low power mode, such as, for example, act like a travel assistant for the user, provide entertainment, and make electronic purchases.