nixos/hardware/device-tree: make overlays more reliable

This make the process of applying overlays more reliable by:

1. Ignoring dtb files that are not really device trees. [^1]

2. Adding a `filter` option (per-overlay, there already is a global one)
   to limit the files to which the overlay applies. This is useful
   in cases where the `compatible` string is ambiguous and multiple
   unrelated files match.

Previously the script would fail in both cases.

[^1]: For example, there is dtbs/overlays/overlay_map.dtb in the
      Raspberry Pi 1 kernel.

1 files changed, 10 insertions, 0 deletions

diff --git a/nixos/modules/hardware/device-tree.nix b/nixos/modules/hardware/device-tree.nix
index 55852776220d3..6204c0fddd037 100644
--- a/nixos/modules/hardware/device-tree.nix
+++ b/nixos/modules/hardware/device-tree.nix
@@ -14,6 +14,15 @@ let
         '';
       };
 
+      filter = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        example = "*rpi*.dtb";
+        description = lib.mdDoc ''
+          Only apply to .dtb files matching glob expression.
+        '';
+      };
+
       dtsFile = mkOption {
         type = types.nullOr types.path;
         description = lib.mdDoc ''
@@ -165,6 +174,7 @@ in
           '';
           type = types.listOf (types.coercedTo types.path (path: {
             name = baseNameOf path;
+            filter = null;
             dtboFile = path;
           }) overlayType);
           description = lib.mdDoc ''