feat(mt8186): initialize platform for MediaTek MT8186

- Add basic platform setup.
- Add MT8186 documentation at docs/plat/.
- Add generic CPU helper functions.
- Add basic register address.

TEST=build pass
BUG=b:202871018

Change-Id: Id3e2f46a8c3ab2f3e29137e508d4c671e8f4aad5
diff --git a/plat/mediatek/mt8186/include/plat_macros.S b/plat/mediatek/mt8186/include/plat_macros.S
new file mode 100644
index 0000000..39727ea
--- /dev/null
+++ b/plat/mediatek/mt8186/include/plat_macros.S
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef PLAT_MACROS_S
+#define PLAT_MACROS_S
+
+#include <platform_def.h>
+
+.section .rodata.gic_reg_name, "aS"
+gicc_regs:
+	.asciz "gicc_hppir", "gicc_ahppir", "gicc_ctlr", ""
+gicd_pend_reg:
+	.asciz "gicd_ispendr regs (Offsets 0x200 - 0x278)\n"	\
+		" Offset:\t\t\tvalue\n"
+newline:
+	.asciz "\n"
+spacer:
+	.asciz ":\t\t0x"
+
+.section .rodata.cci_reg_name, "aS"
+cci_iface_regs:
+	.asciz "cci_snoop_ctrl_cluster0", "cci_snoop_ctrl_cluster1" , ""
+
+	/* ---------------------------------------------
+	 * The below macro prints out relevant GIC
+	 * registers whenever an unhandled exception
+	 * is taken in BL31.
+	 * Clobbers: x0 - x10, x26, x27, sp
+	 * ---------------------------------------------
+	 */
+	.macro plat_crash_print_regs
+	/* TODO: leave implementation to GIC owner */
+	.endm
+
+#endif /* PLAT_MACROS_S */