Initialize platform for MediaTek MT8195

- Add basic platform setup
- Add MT8195 documentation at docs/plat/
- Add generic CPU helper functions
- Add basic register address

Change-Id: I7978e2f32e58900e5cf93f741ee8eaf8b8e3b842
diff --git a/plat/mediatek/mt8195/plat_topology.c b/plat/mediatek/mt8195/plat_topology.c
new file mode 100644
index 0000000..bc95c64
--- /dev/null
+++ b/plat/mediatek/mt8195/plat_topology.c
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch.h>
+#include <arch_helpers.h>
+#include <lib/psci/psci.h>
+
+#include <plat_helpers.h>
+#include <platform_def.h>
+
+const unsigned char mtk_power_domain_tree_desc[] = {
+	/* Number of root nodes */
+	PLATFORM_SYSTEM_COUNT,
+	/* Number of children for the root node */
+	PLATFORM_MCUSYS_COUNT,
+	/* Number of children for the mcusys node */
+	PLATFORM_CLUSTER_COUNT,
+	/* Number of children for the first cluster node */
+	PLATFORM_CLUSTER0_CORE_COUNT,
+};
+
+const unsigned char *plat_get_power_domain_tree_desc(void)
+{
+	return mtk_power_domain_tree_desc;
+}
+
+/*******************************************************************************
+ * This function implements a part of the critical interface between the psci
+ * generic layer and the platform that allows the former to query the platform
+ * to convert an MPIDR to a unique linear index. An error code (-1) is returned
+ * in case the MPIDR is invalid.
+ ******************************************************************************/
+int plat_core_pos_by_mpidr(u_register_t mpidr)
+{
+	unsigned int cluster_id, cpu_id;
+
+	if ((read_mpidr() & MPIDR_MT_MASK) != 0) {
+		/* ARMv8.2 arch */
+		if ((mpidr & (MPIDR_AFFLVL_MASK << MPIDR_AFF0_SHIFT)) != 0) {
+			return -1;
+		}
+		return plat_mediatek_calc_core_pos(mpidr);
+	}
+
+	mpidr &= MPIDR_AFFINITY_MASK;
+
+	if ((mpidr & ~(MPIDR_CLUSTER_MASK | MPIDR_CPU_MASK)) != 0) {
+		return -1;
+	}
+
+	cluster_id = (mpidr >> MPIDR_AFF1_SHIFT) & MPIDR_AFFLVL_MASK;
+	cpu_id = (mpidr >> MPIDR_AFF0_SHIFT) & MPIDR_AFFLVL_MASK;
+
+	if (cluster_id >= PLATFORM_CLUSTER_COUNT) {
+		return -1;
+	}
+
+	/*
+	 * Validate cpu_id by checking whether it represents a CPU in
+	 * one of the two clusters present on the platform.
+	 */
+	if (cpu_id >= PLATFORM_MAX_CPUS_PER_CLUSTER) {
+		return -1;
+	}
+
+	return (cpu_id + (cluster_id * 8));
+}