uart: support light sleep on esp32s3

examples/system/light_sleep/main/timer_wakeup.c

@@ -0,0 +1,18 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+#include "esp_check.h"
+#include "esp_sleep.h"
+
+#define TIMER_WAKEUP_TIME_US    (2 * 1000 * 1000)
+
+static const char *TAG = "timer_wakeup";
+
+esp_err_t example_register_timer_wakeup(void)
+{
+    ESP_RETURN_ON_ERROR(esp_sleep_enable_timer_wakeup(TIMER_WAKEUP_TIME_US), TAG, "Configure timer as wakeup source failed");
+    ESP_LOGI(TAG, "timer wakeup source is ready");
+    return ESP_OK;
+}