How to create the Linux kernel config file when adding a new platform to OpenWrt

I am adding a new platform Nuvoton MA35D1 to OpenWrt 21.02. I find for handling the Linux kernel configuration, the format of raw Linux and OpenWrt are very different.

To create the Linux kernel configuration, I follow the below steps.
(1) Get the workable kernel config file (.config) in raw Linux format
(2) Rename the file .config to be target/linux/ma35d1/$BOARD_NAME/config-5.4
(3) Run "make kernel_menuconfig", and it converts the Linux kernel config (config-5.4) from raw Linux format to OpenWrt format automatically

After the format convert, I find although it can work, but some options are changed. Such as option A is disabled in raw Linux but is enabled in OpenWrt, and option B is enabled in raw Linux but is disabled in OpenWrt. To confirm the features, I need to check and adjust the Linux kernel config manually, and it takes much effort.

Does anyone provides the best solution for how to create the first version of Linux kernel config in OpenWrt?

Chih-Chiang Chang