I'm trying to understand the relationship between embedded RTOSes, SoCs and chip architectures. Specifically, I have a hobby project that would involve me writing a real-time, embedded application for the embox RTOS, and use Arduino hardware for my proof of concept/prototype. Then, budget permitting, I'd like to port that app to run on another, non-Arduino ARM-based system.
My understanding is that ARM is the chip architecture (a conceptual design, really), and that Arduino simply implements this design, and is also a "system on a chip" because it has other things (USB ports, GPIO pins, etc.) that make it more of a computer than just a MCU.
My understanding is that if embox runs on ARM, which they claim it does, then at some point in the future I can take my application and run it on another ARM-based system without any real headache/pain.
Is my understanding of: ARM, Arduino, MCU, SoC and embox/RTOS correct? If not, please clarify/correct me! If so, what sort of considerations would have to be made when porting my app to another ARM system in the future?