radxa/rock-3c: init

Add hardware support module for Radxa Rock 3C SBC (Rockchip RK3566).
- Introduces rockchip/rk3566 platform module exposing
  hardware.rockchip.rk3566.enable.
- New radxa/rock-3c module enables radxa, rk3566, and defaults
  platformFirmware to pkgs.ubootRock3C.

radxa/rock-3c/default.nix

@@ -0,0 +1,22 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+{
+  imports = [
+    ../.
+    ../../rockchip
+  ];
+
+  config = {
+    hardware = {
+      radxa.enable = true;
+      rockchip = {
+        rk3566.enable = true;
+        platformFirmware = lib.mkDefault pkgs.ubootRock3C;
+      };
+    };
+  };
+}