28 minutes ago, sgjava said:

each pinctrl using phandle to identify

Be carefull : phandle can vary between builds, so better use <&pio> and <&r_pio> symbols.

 

30 minutes ago, sgjava said:

So next question is how do I make this part of build process

As I said earlier, append you overlay code in some new board specific patch such as ./patch/kernel/sunxi-dev/nanopi-duo/board-h2plus-nanopi-duo-add-overlay.patch which will also provide change to arch/arm/boot/dts/overlay/Makefile.

@martinayotteI understand the patch part, but usually you make the change somewhere like build/cache/sources/linux-odroidxu4/odroid-5.4.y/arch/arm/boot/dts/exynos5420-pinctrl.dtsi (for XU3/XU4) and a patch is generated in output/patch. This is the step I'm missing. Almost there, thanks for your help do far.

3 hours ago, sgjava said:

This is the step I'm missing.

I'm not understanding exactly.

Maybe because I've always producing patches manually ...

Here is a summary of how I would do it :

(edit the file to add "gpio-line-names" manually)
nano cache/sources/linux-odroidxu4/odroid-5.4.y/arch/arm/boot/dts/exynos5420-pinctrl.dtsi
(save)
pushd cache/sources/linux-odroidxu4/odroid-5.4.y/
git diff arch/arm/boot/dts/exynos5420-pinctrl.dtsi > ~/my-gpio-line-names.patch
popd
mv ~/my-gpio-line-names.patch patches/kernel/odroidxu4-dev/odroidxu4-add-gpio-line-names.patch

 

@martinayotte I'm doing it this way https://github.com/sgjava/patchbian since the build creates the patch for you and a test image at the same time.