Libraries: Add LibDeviceTree for manipulating OpenFirmware Device Trees

Starting with header validation and a dump() method that can be used to
debug future parsing work.

Userland/Libraries/LibDeviceTree/FlattenedDeviceTree.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2021, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Endian.h>
+#include <AK/Types.h>
+
+namespace DeviceTree {
+
+// https://devicetree-specification.readthedocs.io/en/v0.3/flattened-format.html
+struct FlattenedDeviceTreeHeader {
+    BigEndian<u32> magic;             // 0xDOODFEED (BE)
+    BigEndian<u32> totalsize;         // Total size of entire blob including padding b/w and after fields
+    BigEndian<u32> off_dt_struct;     // Offset of StructureBlock from beginning of header
+                                      // https://devicetree-specification.readthedocs.io/en/v0.3/flattened-format.html#sect-fdt-structure-block
+    BigEndian<u32> off_dt_strings;    // Offset of StringsBlock from beginning of header
+                                      // https://devicetree-specification.readthedocs.io/en/v0.3/flattened-format.html#sect-fdt-strings-block
+    BigEndian<u32> off_mem_rsvmap;    // Offset of MemoryReservationBlock from beginning of header
+    BigEndian<u32> version;           // 0.3 spec defines version 17
+    BigEndian<u32> last_comp_version; // 0.3 spec back-compatible with version 16, mandated to be 16
+    BigEndian<u32> boot_cpuid_phys;   // Physical ID given in `reg` property of CPU node of boot cpu
+    BigEndian<u32> size_dt_strings;   // Length in bytes of StringsBlock
+    BigEndian<u32> size_dt_struct;    // Length in bytes of StructureBlock
+};
+static_assert(sizeof(FlattenedDeviceTreeHeader) == 40, "FDT Header size must match specification");
+
+// https://devicetree-specification.readthedocs.io/en/v0.3/flattened-format.html#format
+struct FlattenedDeviceTreeReserveEntry {
+    BigEndian<u64> address;
+    BigEndian<u64> size;
+
+    bool operator==(FlattenedDeviceTreeReserveEntry const& other) const { return other.address == address && other.size == size; }
+    bool operator!=(FlattenedDeviceTreeReserveEntry const& other) const { return !(operator==(other)); }
+};
+static_assert(sizeof(FlattenedDeviceTreeReserveEntry) == 16, "FDT Memory Reservation entry size must match specification");
+
+} // namespace DeviceTree