The overlay works normally in a running system. See this topic. The kernel already has everything, you only need to add the necessary overlay immediately in a working system. No complicated steps with old u-boot scripts are needed. You can change everything on the fly in a running system. https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/dt-overlays.md.html#32-loading-overlays-via-configfs