Kernel/FileSystem: Add the DevLoopFS filesystem

Similarly to DevPtsFS, this filesystem is about exposing loop device
nodes easily in /dev/loop, so userspace doesn't need to do anything in
order to use new devices immediately.

Kernel/FileSystem/DevLoopFS/FileSystem.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2024, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <Kernel/FileSystem/FileSystem.h>
+#include <Kernel/FileSystem/Inode.h>
+
+namespace Kernel {
+
+class LoopDevice;
+class DevLoopFSInode;
+
+class DevLoopFS final : public FileSystem {
+    friend class DevLoopFSInode;
+
+public:
+    virtual ~DevLoopFS() override;
+    static ErrorOr<NonnullRefPtr<FileSystem>> try_create(ReadonlyBytes);
+
+    virtual ErrorOr<void> initialize() override;
+    virtual StringView class_name() const override { return "DevLoopFS"sv; }
+
+    virtual Inode& root_inode() override;
+
+private:
+    virtual u8 internal_file_type_to_directory_entry_type(DirectoryEntryView const& entry) const override;
+
+    DevLoopFS();
+    ErrorOr<NonnullRefPtr<Inode>> get_inode(InodeIdentifier) const;
+
+    RefPtr<DevLoopFSInode> m_root_inode;
+};
+
+}