Kernel: Add support for ACPI Control Method Batteries

The implementation is kinda weird but it exposes some battery
information to userspace!

kernel/include/kernel/ACPI/ACPI.h

@@ -28,6 +28,8 @@ namespace Kernel::ACPI
 		//   2: SAPIC
 		BAN::ErrorOr<void> enter_acpi_mode(uint8_t mode);
 
+		BAN::ErrorOr<void> initialize_acpi_devices();
+
 		BAN::ErrorOr<void> poweroff();
 		BAN::ErrorOr<void> reset();
 

kernel/include/kernel/ACPI/BatterySystem.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <kernel/ACPI/AML/Namespace.h>
+#include <kernel/FS/TmpFS/Inode.h>
+
+namespace Kernel::ACPI
+{
+
+	class BatterySystem
+	{
+		BAN_NON_COPYABLE(BatterySystem);
+		BAN_NON_MOVABLE(BatterySystem);
+	public:
+		static BAN::ErrorOr<void> initialize(AML::Namespace& acpi_namespace);
+
+	private:
+		BatterySystem(AML::Namespace&);
+
+		BAN::ErrorOr<void> initialize_impl();
+
+	private:
+		AML::Namespace& m_acpi_namespace;
+		BAN::RefPtr<TmpDirectoryInode> m_directory;
+	};
+
+}