diff --git a/plat/mediatek/mt8186/include/platform_def.h b/plat/mediatek/mt8186/include/platform_def.h
new file mode 100644
index 0000000..bf1bbef
--- /dev/null
+++ b/plat/mediatek/mt8186/include/platform_def.h
@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef PLATFORM_DEF_H
+#define PLATFORM_DEF_H
+
+#define PLAT_PRIMARY_CPU	0x0
+
+#define MT_GIC_BASE		(0x0C000000)
+#define MCUCFG_BASE		(0x0C530000)
+#define IO_PHYS			(0x10000000)
+
+/* Aggregate of all devices for MMU mapping */
+#define MTK_DEV_RNG0_BASE	IO_PHYS
+#define MTK_DEV_RNG0_SIZE	0x400000
+#define MTK_DEV_RNG1_BASE	(IO_PHYS + 0x1000000)
+#define MTK_DEV_RNG1_SIZE	0xa110000
+#define MTK_DEV_RNG2_BASE	MT_GIC_BASE
+#define MTK_DEV_RNG2_SIZE	0x600000
+
+
+/*******************************************************************************
+ * UART related constants
+ ******************************************************************************/
+#define UART0_BASE			(IO_PHYS + 0x01002000)
+
+#define UART_BAUDRATE			115200
+
+/*******************************************************************************
+ * System counter frequency related constants
+ ******************************************************************************/
+#define SYS_COUNTER_FREQ_IN_TICKS	13000000
+#define SYS_COUNTER_FREQ_IN_MHZ		13
+
+/*******************************************************************************
+ * Platform binary types for linking
+ ******************************************************************************/
+#define PLATFORM_LINKER_FORMAT		"elf64-littleaarch64"
+#define PLATFORM_LINKER_ARCH		aarch64
+
+/*******************************************************************************
+ * Generic platform constants
+ ******************************************************************************/
+#define PLATFORM_STACK_SIZE		0x800
+
+#define FIRMWARE_WELCOME_STR		"Booting Trusted Firmware\n"
+
+#define PLAT_MAX_PWR_LVL		U(3)
+#define PLAT_MAX_RET_STATE		U(1)
+#define PLAT_MAX_OFF_STATE		U(9)
+
+#define PLATFORM_SYSTEM_COUNT		U(1)
+#define PLATFORM_MCUSYS_COUNT		U(1)
+#define PLATFORM_CLUSTER_COUNT		U(1)
+#define PLATFORM_CLUSTER0_CORE_COUNT	U(8)
+#define PLATFORM_CLUSTER1_CORE_COUNT	U(0)
+
+#define PLATFORM_CORE_COUNT		(PLATFORM_CLUSTER0_CORE_COUNT)
+#define PLATFORM_MAX_CPUS_PER_CLUSTER	U(8)
+
+#define SOC_CHIP_ID			U(0x8186)
+
+/*******************************************************************************
+ * Platform memory map related constants
+ ******************************************************************************/
+#define TZRAM_BASE			0x54600000
+#define TZRAM_SIZE			0x00030000
+
+/*******************************************************************************
+ * BL31 specific defines.
+ ******************************************************************************/
+/*
+ * Put BL3-1 at the top of the Trusted SRAM (just below the shared memory, if
+ * present). BL31_BASE is calculated using the current BL3-1 debug size plus a
+ * little space for growth.
+ */
+#define BL31_BASE			(TZRAM_BASE + 0x1000)
+#define BL31_LIMIT			(TZRAM_BASE + TZRAM_SIZE)
+
+/*******************************************************************************
+ * Platform specific page table and MMU setup constants
+ ******************************************************************************/
+#define PLAT_PHY_ADDR_SPACE_SIZE	(1ULL << 32)
+#define PLAT_VIRT_ADDR_SPACE_SIZE	(1ULL << 32)
+#define MAX_XLAT_TABLES			16
+#define MAX_MMAP_REGIONS		16
+
+/*******************************************************************************
+ * Declarations and constants to access the mailboxes safely. Each mailbox is
+ * aligned on the biggest cache line size in the platform. This is known only
+ * to the platform as it might have a combination of integrated and external
+ * caches. Such alignment ensures that two maiboxes do not sit on the same cache
+ * line at any cache level. They could belong to different cpus/clusters &
+ * get written while being protected by different locks causing corruption of
+ * a valid mailbox address.
+ ******************************************************************************/
+#define CACHE_WRITEBACK_SHIFT		6
+#define CACHE_WRITEBACK_GRANULE		(1 << CACHE_WRITEBACK_SHIFT)
+#endif /* PLATFORM_DEF_H */