nixos/kernel: better docs for boot.kernelPatches

    boot.kernelPatches = mkOption {

      type = types.listOf types.attrs;

      default = [];

      example = literalExpression "[ pkgs.kernelPatches.ubuntu_fan_4_4 ]";

      description = lib.mdDoc "A list of additional patches to apply to the kernel.";

      example = literalExpression ''

        [

          {

            name = "foo";

            patch = ./foo.patch;

            structuredExtraConfig.FOO = lib.kernel.yes;

            features.foo = true;

          }

        ]

      '';

      description = lib.mdDoc ''

        A list of additional patches to apply to the kernel.

        Every item should be an attribute set with the following attributes:

        ```nix

        {

          name = "foo";                 # descriptive name, required

          patch = ./foo.patch;          # path or derivation that contains the patch source

                                        # (required, but can be null if only config changes

                                        # are needed)

          structuredExtraConfig = {     # attrset of extra configuration parameters

            FOO = lib.kernel.yes;       # (without the CONFIG_ prefix, optional)

          };                            # values should generally be lib.kernel.yes or lib.kernel.no

          features = {                  # attrset of extra "features" the kernel is considered to have

            foo = true;                 # (may be checked by other NixOS modules, optional)

          };

          extraConfig = "CONFIG_FOO y"; # extra configuration options in string form

                                        # (deprecated, use structuredExtraConfig instead, optional)

        }

        ```

        There's a small set of existing kernel patches in Nixpkgs, available as `pkgs.kernelPatches`,

        that follow this format and can be used directly.

      '';

    };

    boot.kernel.randstructSeed = mkOption {