diff --git a/drivers/gpu/drm/xe/abi/xe_sysctrl_abi.h b/drivers/gpu/drm/xe/abi/xe_sysctrl_abi.h
new file mode 100644
index 000000000000..4cbde267ac44
--- /dev/null
+++ b/drivers/gpu/drm/xe/abi/xe_sysctrl_abi.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2026 Intel Corporation
+ */
+
+#ifndef _XE_SYSCTRL_ABI_H_
+#define _XE_SYSCTRL_ABI_H_
+
+#include <linux/types.h>
+
+/**
+ * DOC: System Controller ABI
+ *
+ * This header defines the Application Binary Interface (ABI) used by
+ * drm/xe to communicate with System Controller firmware on Intel Xe3p
+ * discrete GPU platforms.
+ *
+ * System Controller (sysctrl) is a firmware-managed entity on Intel
+ * dGPUs responsible for certain low-level platform management
+ * functions.
+ *
+ * Communication protocol:
+ *
+ * Communication uses a mailbox interface with messages composed of:
+ *
+ * - Application message header (struct xe_sysctrl_app_msg_hdr)
+ *   containing group_id, command, and version
+ * - Variable-length, command-specific payload
+ *
+ * Message header format:
+ *
+ * The 32-bit application message header is packed as:
+ *
+ * - Bits [7:0]   : Group ID identifying command group
+ * - Bits [15:8]  : Command identifier within group
+ * - Bits [23:16] : Command version for interface compatibility
+ * - Bits [31:24] : Reserved, must be zero
+ *
+ * This header defines firmware ABI message formats and constants shared
+ * between driver and System Controller firmware.
+ */
+
+/**
+ * struct xe_sysctrl_app_msg_hdr - Application layer message header
+ * @data: 32-bit header data
+ *
+ * Header structure for application-level messages.
+ */
+struct xe_sysctrl_app_msg_hdr {
+	u32 data;
+} __packed;
+
+#define SYSCTRL_HDR_GROUP_ID_MASK	GENMASK(7, 0)
+#define SYSCTRL_HDR_COMMAND_MASK	GENMASK(14, 8)
+#define SYSCTRL_HDR_COMMAND_MAX		0x7f
+#define SYSCTRL_HDR_IS_RESPONSE		BIT(15)
+#define SYSCTRL_HDR_RESERVED_MASK	GENMASK(23, 16)
+#define SYSCTRL_HDR_RESULT_MASK		GENMASK(31, 24)
+
+#define APP_HDR_GROUP_ID_MASK		GENMASK(7, 0)
+#define APP_HDR_COMMAND_MASK		GENMASK(15, 8)
+#define APP_HDR_VERSION_MASK		GENMASK(23, 16)
+#define APP_HDR_RESERVED_MASK		GENMASK(31, 24)
+
+#endif
diff --git a/drivers/gpu/drm/xe/xe_sysctrl_mailbox.h b/drivers/gpu/drm/xe/xe_sysctrl_mailbox.h
new file mode 100644
index 000000000000..91460be9e22c
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_sysctrl_mailbox.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2026 Intel Corporation
+ */
+
+#ifndef _XE_SYSCTRL_MAILBOX_H_
+#define _XE_SYSCTRL_MAILBOX_H_
+
+#include <linux/bitfield.h>
+#include <linux/types.h>
+
+#include "abi/xe_sysctrl_abi.h"
+
+struct xe_sysctrl;
+struct xe_sysctrl_mailbox_command;
+
+#define XE_SYSCTRL_APP_HDR_GROUP_ID(hdr) \
+	FIELD_GET(APP_HDR_GROUP_ID_MASK, le32_to_cpu((hdr)->data))
+
+#define XE_SYSCTRL_APP_HDR_COMMAND(hdr) \
+	FIELD_GET(APP_HDR_COMMAND_MASK, le32_to_cpu((hdr)->data))
+
+#define XE_SYSCTRL_APP_HDR_VERSION(hdr) \
+	FIELD_GET(APP_HDR_VERSION_MASK, le32_to_cpu((hdr)->data))
+
+void xe_sysctrl_mailbox_init(struct xe_sysctrl *sc);
+int xe_sysctrl_send_command(struct xe_sysctrl *sc,
+			    struct xe_sysctrl_mailbox_command *cmd,
+			    size_t *rdata_len);
+
+#endif
diff --git a/drivers/gpu/drm/xe/xe_sysctrl_mailbox_types.h b/drivers/gpu/drm/xe/xe_sysctrl_mailbox_types.h
new file mode 100644
index 000000000000..89456aec6097
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_sysctrl_mailbox_types.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2026 Intel Corporation
+ */
+
+#ifndef _XE_SYSCTRL_MAILBOX_TYPES_H_
+#define _XE_SYSCTRL_MAILBOX_TYPES_H_
+
+#include <linux/types.h>
+
+#include "abi/xe_sysctrl_abi.h"
+
+/**
+ * struct xe_sysctrl_mailbox_command - System Controller mailbox command
+ */
+struct xe_sysctrl_mailbox_command {
+	/** @header: Application message header containing command information */
+	struct xe_sysctrl_app_msg_hdr header;
+
+	/** @data_in: Pointer to input payload data (can be NULL if no input data) */
+	void *data_in;
+
+	/** @data_in_len: Size of input payload in bytes (0 if no input data) */
+	size_t data_in_len;
+
+	/** @data_out: Pointer to output buffer for response data (can be NULL if no response) */
+	void *data_out;
+
+	/** @data_out_len: Size of output buffer in bytes (0 if no response expected) */
+	size_t data_out_len;
+};
+
+#define XE_SYSCTRL_MB_FRAME_SIZE	16
+#define XE_SYSCTRL_MB_MAX_FRAMES	64
+#define XE_SYSCTRL_MB_MAX_MESSAGE_SIZE	\
+	(XE_SYSCTRL_MB_FRAME_SIZE * XE_SYSCTRL_MB_MAX_FRAMES)
+
+#define XE_SYSCTRL_MB_DEFAULT_TIMEOUT_MS	500
+
+#endif