feat(mt8188): initialize platform for MediaTek MT8188

- Add basic platform setup.
- Add MT8188 documentation at docs/plat/.
- Add generic CPU helper functions.
- Add basic register address.
- Add mtk_pm.c in lib/pm

TEST=build pass
BUG=b:236331724

Change-Id: I5f8617c42ffba2c9d3a16f3980cb75fda5624031
diff --git a/plat/mediatek/lib/pm/rules.mk b/plat/mediatek/lib/pm/rules.mk
new file mode 100644
index 0000000..77d0408
--- /dev/null
+++ b/plat/mediatek/lib/pm/rules.mk
@@ -0,0 +1,14 @@
+#
+# Copyright (c) 2022, MediaTek Inc. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+#
+
+LOCAL_DIR := $(call GET_LOCAL_DIR)
+
+MODULE := pm
+
+LOCAL_SRCS-y := ${LOCAL_DIR}/mtk_pm.c
+
+$(eval $(call MAKE_MODULE,$(MODULE),$(LOCAL_SRCS-y),$(MTK_BL)))