How to select board config
We use opensource idbloader(See Boot_option) on some chips (rk3036, rk3288) and its dmc driver can't support ddr-type autodetct, so the wrong ddr dts settings will make the board failed to enter u-boot.
PMIC setting usually doesn't matter in u-boot, but for the board with rk818, USB input current should be configured before enter u-boot.
Some board have disable emmc in u-boot for convenience, though the hardware actually have emmc, please note it. (firefly-rk3288）