Isolated subproject (does not touch home:realni/linux-up-cpufreq). Runs dtschema's dt-doc-validate over the three DT schema files the up/cpufreq-mt6797 series touches. dtschema is pulled from the third-party home:Jianhua:devel-tools (python313-dtschema, Provides python3-dtschema) layered over openSUSE:Factory, because python3-dtschema is not available on this OBS's Debian:13 nor as any published .deb, and OBS build roots are offline (no pip).