What is little kernel?

Little Kernel is an operating system used in small embedded devices, bootloaders, etc. It is mainly used where OS primitives like threads, mutexes, and timers are needed. This tiny OS keeps things small and lightweight. They come in small sizes such as 15-20 B in embedded ARM platforms. They are now used in Android bootloader and as default bootloader in some ARM SoC manufacturers. Zircon, a microkernel used in Fuchsia Operating System also based on Little kernel.