Yeah, even a small part such as the cc1310 from Texas Instruments (a sub-GHz wireless SOC for <10USD MOQ-1) is a triple-core device. One Cortex-M3 as the main core, a Cortex-something as the radio core, and a Sensor Controller (I'm guessing msp430-derived) as a low-power helper core. For the latter, you actually compile a binary blob that you push to it in firmware, and the format is not ARM.

Quite complex stuff.