Got invited to ARM's hq in Cambridge 1-2 months after applying. I was interviewed by one of their hardware engineers. He asked me first if I knew VHDL which I didn't at the time so he asked me to write a program C. He then asked me optimise the program (remove redundant statements to make it faster etc.). As some counting was being performed in the program, I was asked to design a digital counter that could perform such a function.

Lastly he asked me to draw the internals of an SoC (System on Chip).

A bit surprised by the SoC questions. I would advise people to look up SoC architectures from companies like Qualcomm etc.