For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tiwai:kernel:4.9/standard/home:tiwai:kernel:4.9.repo
zypper refresh
zypper install kernel-docs
For PPC run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tiwai:kernel:4.9/PPC/home:tiwai:kernel:4.9.repo
zypper refresh
zypper install kernel-docs
For ARM run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:tiwai:kernel:4.9/ARM/home:tiwai:kernel:4.9.repo
zypper refresh
zypper install kernel-docs