Why do I get errors while compiling the kernel?

Question

linux

The source was taken from the official github. Xiaomi mi 8 lite. Without changing anything in menuconfig all the same errors. Can anyone tell me how to build the kernel correctly.
What I entered:
1. In .bashrc: export ARCH=arm64
export SUBARCH=arm64
export CROSS_COMPILE=/root/kernel_dev/gcc-linaro-4.9.4-2017.01-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-
2. make platina_user_defconfig
3. cp .config arch/arm64/configs/patina_defconfig
3. make platina_defconfig
4. make -j5 Type
errors:
In file included from drivers/bluetooth/btfm_slim.c:27:0:
drivers/bluetooth/btfm_slim_wcn3990 .h:15:23: fatal error: btfm_slim.h: No such file or directory
Although the btfm_slim.c file exists, but for some reason it does not see it.
In short, it's not clear why the errors are if the source is OFFICIAL. Maybe I'm doing something wrong, who can tell me?

Answer 1

Maybe I'm doing something wrong, who can tell me?

Everything is so (except that it makes no sense to call one defconfig, then copy its results and call it again. But there should be no harm from this either. By the way, cp .config arch/arm64/configs/ patina _defconfig ; make platina _defconfig - sealed up asking a question?).
Try to collect out-of-tree, sometimes it helps. To do this, add O=<путь к каталогу сборки>to all make commands.
Well, or give a link to the repository and the tag or branch from which you need to collect - I'll try too.