Renesas provides the R-Car S4 SDK, software that runs on the R-Car S4 SoC.
This video, Part 3 of Linux BSP setup in the 'R-Car S4 Startup Guide', explains 'Boot Kernel by using eMMC' as the following steps.
- Prepare image, DTB files, and userland to NFS.
- Write image files and userland to eMMC.
- Boot Kernel for board S4 by using eMMC.