Porting Raspberry Pi 3 has many issues. Zephyr OS does not support the Raspberry Pi 3. The Raspberry Pi 3 is a different ARM architecture than what we currently have support for. The Raspberry Pi 3 is Cortex A5, we currently support a few Cortex M versions. Adding support for another architecture is a major undertaking. This is just the SoC issue. The next problem with porting for the Raspberry Pi 3 board is that you don't have schematics. This means you can't support any of the hardware on the board. The schematics for Raspberry Pi boards are proprietary and are not released to the public at all. Do you work for Raspberry Pi Organization? If not, I doubt you can get the schematics.