It compiles...

.gitignore

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+/result*

default.nix

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+let
+  pkgs = (import <nixos-unstable> { }).pkgsCross.aarch64-multiplatform;
+  ubootDerivations = pkgs.callPackage ./uboot-quartz64.nix { };
+in
+{
+  ubootSoQuartz = ubootDerivations.ubootSoQuartz;
+  ubootQuartz64a = ubootDerivations.ubootQuartz64a;
+  ubootQuartz64b = ubootDerivations.ubootQuartz64b;
+}

uboot-quartz64.nix

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+{ lib
+, fetchFromGitHub
+, buildUBoot
+}:
+
+let
+  bl31Blobs = fetchFromGitHub {
+    owner = "JeffyCN";
+    repo = "rockchip_mirrors";
+    rev = "6186debcac95553f6b311cee10669e12c9c9963d";
+    sha256 = "nH/g95QMv0bFgbT5jiKTAa3Vd0gnqtG4M6nkZ5R3S0E=";
+  };
+  rkbinBlobs = fetchFromGitHub {
+    owner = "rockchip-linux";
+    repo = "rkbin";
+    rev = "a4c6de9ea29f275bb1d08c94ccded51ff2ab5b92";
+    sha256 = "e3RH/4hi+xc5cQpzt2txyZYNMGQvC1jGDJpzBY2QSHo=";
+  };
+  buildQuartz64UBoot = (defconfig: buildUBoot {
+    version = "2022.64-rc1";
+    defconfig = defconfig;
+    src = fetchFromGitHub {
+      owner = "CounterPillow";
+      repo = "u-boot-quartz64";
+      rev = "87c317f72735f9b336c55b9e00222e71816040e7";
+      sha256 = "mmy6fY6+7aVSdYr/pZCX2kTP7/Zj3Ib1uBN9gFWFoxw=";
+    };
+    extraMakeFlags = [
+      "ARCH=arm"
+    ];
+    extraMeta = {
+      platforms = [ "aarch64-linux" ];
+      license = lib.licenses.unfreeRedistributableFirmware;
+    };
+    filesToInstall = [ "u-boot.itb" "idbloader.img" ];
+    preConfigure = ''
+      make mrproper
+
+      cp "${bl31Blobs}/bin/rk35/rk3568_bl31_v1.28.elf" "bl31.elf"
+      cp "${rkbinBlobs}/bin/rk35/rk3566_ddr_1056MHz_v1.13.bin" ram_init.bin
+    '';
+  });
+in
+{
+  ubootSoQuartz = buildQuartz64UBoot "soquartz-rk3566_defconfig";
+  ubootQuartz64b = buildQuartz64UBoot "quartz64-b-rk3566_defconfig";
+  ubootQuartz64a = buildQuartz64UBoot "quartz64-a-rk3566_defconfig";
+}