Hello Masahiro,
Fedora ships vmlinux, config, System.map in the module directory. Why don't you mimic it? Change the %install section to install them to /lib/modules/%{KERNELRELEASE}/.
Ok, I did not dare to change a lot of things, overall in other sections. I like the idea of imitating Fedora and making it easier.
Then, change %post section to copy them to /boot/. If you take care of an unusual case where installkernel is not found, you can support manual copy as a fallback.
Ok, much clear in this way (and independent of software packages). Again, good idea.
Maybe, you can also convert the installkernel syntax to kernel-install while you are here.
Ok, that tool is more complete, I will try.
The next version will include all of this.
Thank you
Best rgards José Ignacio