add module for device-specific config

in principle this module declares the config that's defined in
devices/foo/default.nix

modules/hardware.nix

@@ -0,0 +1,36 @@
+{ lib, pkgs, config, ...}:
+let
+  inherit (lib) mkEnableOption mkOption types isDerivation hasAttr ;
+in {
+  options = {
+    boot = {
+      dts = {
+        src = mkOption { type = types.path; };
+        includes = mkOption {
+          default = [];
+          type = types.listOf types.path;
+        };
+      };
+    };
+    device = {
+      defaultOutput = mkOption {
+        type = types.nonEmptyStr;
+      };
+      flash = {
+        address = mkOption { type = types.str; };
+        size = mkOption { type = types.str; };
+      };
+      loadAddress = mkOption { default = null; };
+      entryPoint = mkOption { };
+      radios = mkOption {
+        type = types.listOf types.str;
+        default = [];
+        example = ["ath9k" "ath10k"];
+      };
+      rootDevice = mkOption { };
+      networkInterfaces = mkOption {
+        type = types.attrsOf types.anything;
+      };
+    };
+  };
+}