Are there regulations for unmanned aerial systems avionics?
The flight control software on military grade UAV/UAS has DO-178/DO-254 requirements, per briefings I attended, and also that software provided for embedding in those had to meet those and other requirements.

I am not an expert on the UAS platform we used (Global Hawk RQ-4) but it is safe to say that it is a complex bird with multiple capabilities. A typical mission flight crew consisted of a launch and recovery pilot, and mission pilots and sensor operators, in sufficient numbers to handle extended missions.  

I am unaware of any consumer grade UAS utilizing those standards, and doubt there are many, if any at all, due to the increased development cost. I am unaware of any type certificated sUAS.

To give you an example, I had a certain nav sensor related function integrated for VFR use on a sensor platform (Twin Otter).  The development cost was about 4.5 million. If we were to apply the standards so that we could operate that platform in an IFR environment, the estimated cost was about 9.5 to 11 million.  Sure there were just a few additional capabilities, but a big part of it was systems engineering and test.