OS kernel on embedded ARM64 systems requires PSCI interface to bring CPU cores up/down, suspend/resume/reset/power off. U-Boot bootloader provides a PSCI interface and this talk explains it. The talk consists of five parts -- how the PSCI interface works, where and how OS kernel calls it, how and in which hooks on the bootloader side do those calls land, and how those hooks in U-Boot provide functionality required by OS. Last part is an example of U-Boot configured to provide PSCI interface on contemporary SoC . The benefit of using the U-Boot PSCI interface over other PSCI interface providers is twofold. First, it allows for utilizing the full potential of U-Boot, and especially the SPL preloader, which can then boot OS kernel directly and quickly. Second, removing one software component from the boot stack reduces the Software BoM.