That's a patch, not an actual dts. That patch modifies a Make file and creates a dts file. The patch is part of a much larger build. You can see an extra line being added into the Make file, (used to compile the new dts along with other dts's). This is similar to the way Armbian build would do it, with one of the build scripts actually doing the compiling of all of the dtb's.
A possible way to do this would be to set up Armbian build and add the patch into build/patch/kernel/rockchip64-current.
You would need to manually modify the make part to match the Make file in /build/cache/sources/linux-mainline/linux-5.15.y/arch/arm64/boot/dts/rockchip.
Or a better way would be to use the CREATE_PATCHES=yes build option which would stop the build and allow you to modify the Make file then create a patch for you (second stop for kernel). You could then use that patch to modify your original patch and build orangepi-R1plus-lts and the dtb will be compiled and end up with the others. But you may not need to do any of that.
While looking up the patch path for this reply, I noticed a patch in Armbian Build called add-board-nanopi-r2c.patch.
So I used the build menu (which I seldom do) and there is actually a build option for nanopi-r2c (it's not on the download list, implying that it's unsupported, and it's probably in the wrong menu (someone probably missed it when the menu's were split) and who knows if it has survived uBoot and kernel upgrades. I see no archived builds, also implying that it's unsupported. I've requested clarification of it's status, so it's likely to move to community support in the other (CSC/WIP/EOS/TVB) menu. Unsupported boards are " build your own" only.
I suggest that you set up Armbian build and try to build it.
You can use my instructions a few replies above either on an Ubuntu based PC or virtual machine.
Edit: I built it. One time only, it ties up my pc for an hour. Let me know if it works.
https://drive.google.com/file/d/1nSug6EYF6O6CALLCaZA1PqRZE5VUBI2n/view?usp=sharing
Or if you run a recent version of Ubuntu or a derivative like Mint then you can use the Armbian build system. It's pretty easy.
(Officially supported version is currently Ubuntu Jammy, but others are unofficially allowed (without support), and for others not on the allowed list, the OS check can be bypassed).
Log in as root (sudo su) and run:
$ mkdir /build-armbian (wherever you want and named whatever you want)
$ cd /build-armbian
$ apt-get -y -qq install git
$ git clone --depth 1 https://github.com/armbian/build
$ cd build
Run the script
$ ./compile.sh
Follow the menu's (build time is slower the first time because it downloads, compiles, and builds caches, (and cpu power makes a big difference)
