ipc: introduce IPC message service

This introduces a new IPC mechanism: IPC message service, where
IPC transactions are centered around messages instead of raw
byte streams. This provides a bit more clarity in the code as
this shows what type of message is being sent. This also allows
backend to select the delivery mechanism based on the message
type for supported hardware.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

Author: dcpleung

include/zephyr/ipc/ipc_msg_evts.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2025 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_IPC_IPC_MSG_EVTS_H_
+#define ZEPHYR_INCLUDE_IPC_IPC_MSG_EVTS_H_
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief IPC Message Service Event Types
+ * @defgroup ipc_msg_service_evt_types IPC Message Service Event Types
+ * @ingroup ipc_msg_service_api
+ * @{
+ */
+
+enum ipc_msg_evts {
+	/**
+	 * Start event type number for common event types.
+	 *
+	 * @note Starting at 1 to avoid having a type with value 0.
+	 */
+	IPC_MSG_EVT_COMMON_START = 1,
+
+	/** Remote has acknowleged the message. */
+	IPC_MSG_EVT_REMOTE_ACK = IPC_MSG_EVT_COMMON_START,
+
+	/** Remote has done processing the message. */
+	IPC_MSG_EVT_REMOTE_DONE,
+
+	/** Max number for common event types. */
+	IPC_MSG_EVT_COMMON_MAX,
+
+	/** Starting number to define custom event types. */
+	IPC_MSG_EVT_CUSTOM_START = 128,
+
+	/** Maximum number of event types. */
+	IPC_MSG_EVT_MAX = 255
+};
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_IPC_IPC_MSG_EVTS_H_ */

include/zephyr/ipc/ipc_msg_queries.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2025 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_IPC_IPC_MSG_QUERIES_H_
+#define ZEPHYR_INCLUDE_IPC_IPC_MSG_QUERIES_H_
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief IPC Message Service Query Types
+ * @defgroup ipc_msg_service_query_types IPC Message Service Query Types
+ * @ingroup ipc_msg_service_api
+ * @{
+ */
+
+enum ipc_msg_queries {
+	/**
+	 * Start event type number for common query types.
+	 *
+	 * @note Starting at 1 to avoid having a type with value 0.
+	 */
+	IPC_MSG_QUERY_COMMON_START = 1,
+
+	/**
+	 * Ask if the backend is ready.
+	 *
+	 * Returns 0 if backend is ready. Negative value if not.
+	 */
+	IPC_MSG_QUERY_IS_READY = IPC_MSG_QUERY_COMMON_START,
+
+	/** Max number for common query types. */
+	IPC_MSG_QUERY_COMMON_MAX,
+
+	/** Starting number to define custom query types. */
+	IPC_MSG_QUERY_CUSTOM_START = 128,
+
+	/** Maximum number of query types. */
+	IPC_MSG_QUERY_MAX = 255
+};
+
+/**
+ * @}
+ */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_IPC_IPC_MSG_QUERIES_H_ */