diff --git a/plat/meson/gxl/gxl_def.h b/plat/meson/gxl/gxl_def.h
new file mode 100644
index 0000000..ada2656
--- /dev/null
+++ b/plat/meson/gxl/gxl_def.h
@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef GXBB_DEF_H
+#define GXBB_DEF_H
+
+#include <lib/utils_def.h>
+
+/*******************************************************************************
+ * System oscillator
+ ******************************************************************************/
+#define GXBB_OSC24M_CLK_IN_HZ			ULL(24000000) /* 24 MHz */
+
+/*******************************************************************************
+ * Memory regions
+ ******************************************************************************/
+#define GXBB_NSDRAM0_BASE			UL(0x01000000)
+#define GXBB_NSDRAM0_SIZE			UL(0x0F000000)
+
+#define GXBB_NSDRAM1_BASE			UL(0x10000000)
+#define GXBB_NSDRAM1_SIZE			UL(0x00100000)
+
+#define BL31_BASE				UL(0x05100000)
+#define BL31_SIZE				UL(0x000C0000)
+#define BL31_LIMIT				(BL31_BASE + BL31_SIZE)
+
+/* Shared memory used for SMC services */
+#define GXBB_SHARE_MEM_INPUT_BASE		UL(0x050FE000)
+#define GXBB_SHARE_MEM_OUTPUT_BASE		UL(0x050FF000)
+
+#define GXBB_SEC_DEVICE0_BASE			UL(0xC0000000)
+#define GXBB_SEC_DEVICE0_SIZE			UL(0x09000000)
+
+#define GXBB_SEC_DEVICE1_BASE			UL(0xD0040000)
+#define GXBB_SEC_DEVICE1_SIZE			UL(0x00008000)
+
+#define GXBB_TZRAM_BASE				UL(0xD9000000)
+#define GXBB_TZRAM_SIZE				UL(0x00014000)
+/* Top 0xC000 bytes (up to 0xD9020000) used by BL2 */
+
+/* Mailboxes */
+#define GXBB_MHU_SECURE_SCP_TO_AP_PAYLOAD	UL(0xD9013800)
+#define GXBB_MHU_SECURE_AP_TO_SCP_PAYLOAD	UL(0xD9013A00)
+#define GXBB_PSCI_MAILBOX_BASE			UL(0xD9013F00)
+
+// * [	 1K]	0xD901_3800 - 0xD901_3BFF	Secure Mailbox (3)
+// * [	 1K]	0xD901_3400 - 0xD901_37FF	High Mailbox (2) *
+// * [	 1K]	0xD901_3000 - 0xD901_33FF	High Mailbox (1) *
+
+#define GXBB_TZROM_BASE				UL(0xD9040000)
+#define GXBB_TZROM_SIZE				UL(0x00010000)
+
+#define GXBB_SEC_DEVICE2_BASE			UL(0xDA000000)
+#define GXBB_SEC_DEVICE2_SIZE			UL(0x00200000)
+
+#define GXBB_SEC_DEVICE3_BASE			UL(0xDA800000)
+#define GXBB_SEC_DEVICE3_SIZE			UL(0x00200000)
+
+/*******************************************************************************
+ * GIC-400 and interrupt handling related constants
+ ******************************************************************************/
+#define GXBB_GICD_BASE				UL(0xC4301000)
+#define GXBB_GICC_BASE				UL(0xC4302000)
+
+#define IRQ_SEC_PHY_TIMER			29
+
+#define IRQ_SEC_SGI_0				8
+#define IRQ_SEC_SGI_1				9
+#define IRQ_SEC_SGI_2				10
+#define IRQ_SEC_SGI_3				11
+#define IRQ_SEC_SGI_4				12
+#define IRQ_SEC_SGI_5				13
+#define IRQ_SEC_SGI_6				14
+#define IRQ_SEC_SGI_7				15
+
+/*******************************************************************************
+ * UART definitions
+ ******************************************************************************/
+#define GXBB_UART0_AO_BASE			UL(0xC81004C0)
+#define GXBB_UART0_AO_CLK_IN_HZ			GXBB_OSC24M_CLK_IN_HZ
+#define GXBB_UART_BAUDRATE			U(115200)
+
+/*******************************************************************************
+ * Memory-mapped I/O Registers
+ ******************************************************************************/
+#define GXBB_AO_TIMESTAMP_CNTL			UL(0xC81000B4)
+
+#define GXBB_SYS_CPU_CFG7			UL(0xC8834664)
+
+#define GXBB_AO_RTI_STATUS_REG3			UL(0xDA10001C)
+
+#define GXBB_HIU_MAILBOX_SET_0			UL(0xDA83C404)
+#define GXBB_HIU_MAILBOX_STAT_0			UL(0xDA83C408)
+#define GXBB_HIU_MAILBOX_CLR_0			UL(0xDA83C40C)
+#define GXBB_HIU_MAILBOX_SET_3			UL(0xDA83C428)
+#define GXBB_HIU_MAILBOX_STAT_3			UL(0xDA83C42C)
+#define GXBB_HIU_MAILBOX_CLR_3			UL(0xDA83C430)
+
+/*******************************************************************************
+ * System Monitor Call IDs and arguments
+ ******************************************************************************/
+#define GXBB_SM_GET_SHARE_MEM_INPUT_BASE	U(0x82000020)
+#define GXBB_SM_GET_SHARE_MEM_OUTPUT_BASE	U(0x82000021)
+
+#define GXBB_SM_EFUSE_READ			U(0x82000030)
+#define GXBB_SM_EFUSE_USER_MAX			U(0x82000033)
+
+#define GXBB_SM_JTAG_ON				U(0x82000040)
+#define GXBB_SM_JTAG_OFF			U(0x82000041)
+
+#define GXBB_JTAG_STATE_ON			U(0)
+#define GXBB_JTAG_STATE_OFF			U(1)
+
+#define GXBB_JTAG_M3_AO				U(0)
+#define GXBB_JTAG_M3_EE				U(1)
+#define GXBB_JTAG_A53_AO			U(2)
+#define GXBB_JTAG_A53_EE			U(3)
+
+#endif /* GXBB_DEF_H */