feat(openthread): support multipan feature for host device

components/openthread/include/esp_radio_spinel_multipan.h

@@ -0,0 +1,60 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include "esp_err.h"
+#include "esp_openthread_types.h"
+#include "esp_radio_spinel.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Multipan host radio backend.
+ *
+ * One physical UART RCP link is owned by this module. Incoming spinel frames
+ * are fanned out into per-client queues.
+ */
+typedef struct {
+    esp_openthread_radio_mode_t radio_mode;           /*!< Must be RADIO_MODE_UART_RCP */
+    esp_radio_spinel_uart_config_t radio_uart_config; /*!< UART RCP */
+} esp_radio_spinel_multipan_radio_config_t;
+
+/**
+ * @brief Initialize the shared RCP backend.
+ *
+ * Currently only `RADIO_MODE_UART_RCP` is supported. This function is expected
+ * to be called once; a second call is rejected. Call this before starting the
+ * OpenThread or Zigbee stacks so they can attach as clients.
+ *
+ * @param[in]  radio_config  Radio backend configuration. Must not be NULL.
+ *                           `radio_mode` must be `RADIO_MODE_UART_RCP`.
+ *
+ * @return
+ *      - ESP_OK on success
+ *      - ESP_ERR_INVALID_ARG if `radio_config` is NULL
+ *      - ESP_ERR_INVALID_STATE if the backend is already initialized
+ *      - ESP_ERR_NOT_SUPPORTED if `radio_mode` is not `RADIO_MODE_UART_RCP`
+ *      - ESP_ERR_NO_MEM if a lock, queue, or task cannot be created
+ *      - ESP_FAIL on other failures
+ */
+esp_err_t esp_radio_spinel_multipan_init(const esp_radio_spinel_multipan_radio_config_t *radio_config);
+
+/**
+ * @brief Tear down the backend. All client fds must already be closed.
+ *
+ * @return
+ *      - ESP_OK on success
+ *      - ESP_ERR_INVALID_STATE if the backend is not initialized, or if any
+ *        client is still open
+ */
+esp_err_t esp_radio_spinel_multipan_deinit(void);
+
+#ifdef __cplusplus
+}
+#endif