How many categories are hardware engineers divided into?

Learning ARM, from a hardware perspective, means learning interface circuit design on the one hand, and board-level programming in assembly and C language on the other. From a software perspective, it is necessary to learn the driver and transplantation of the operating system level based on ARM processors. These must be clear for beginners, either starting from the hardware, or starting from the familiarity of the operating system to the application, but no matter what you learn, as long as it is not pure API-based application layer programming above the operating system level, hardware You still need to be able to understand things like registers, and you still need to know board-level assembly and C programming. Therefore, for those who are interested in the hardware layer and driver of embedded systems, ARM's interface circuit design, ARM's C language and assembly language programming and debugging development environment still need to be mastered.