ARM is a processor architecture implemented in various (often incompatible) chipsets and devices running various operating systems.
There are some libraries related to the embedded target providing access to the hardware most ARM microcontrollers provide. If you run a full Linux on your ARM processor, it's best to use the Linux' way to handle the hardware - see Raspberry Pi#Accessing external hardware for more information.
- Pascal port of the STM32F7xx_HAL
- Realtime OS for embedded systems, currently supports ARMv4T, ARMv6, AVR