I am trying to develop an out-of-tree driver kernel module and an application using buildroot Linux, which implement ioctl like control from user space to kernel space. I want to make user space and kernel space share same data structure, which is supposed to be placed at uapi folder, I found all uapi folders are under output/build/linux-5.15 for my case, even I place my new header at output/build/linux-5.15/include/uapi or output/build/linux-5.15/arch/arm/include/uapi, but the 'make' will not compile files at output/build/linux-5.15, where should I put the new data strut header file for out-of-tree module, such as cirosantilli's kernel_module example (How to add a Linux kernel driver module as a Buildroot package?).