[throwaypestban]

> the baseband chip in your smartphone runs it's own ...

Microkernel

In many if not most cases this kernel would be an L4 implementation.

> OKL4 has been deployed on over 2 billion mobile phones (https://en.wikipedia.org/wiki/Open_Kernel_Labs)

[monocasa]

Modern hexagons run a full Linux under L4 also. It seems like the microkernel separation isn't really architected towards security AFAICT, but for running hard real time tasks on the same cores as the rest of the system.