esp_hw_support: Move rtc.h header from target components

components/esp_hw_support/include/soc/esp32/rtc.h

@@ -0,0 +1,31 @@
+/*
+ * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file esp32/rtc.h
+ *
+ * This file contains declarations of rtc related functions.
+ */
+
+/**
+ * @brief Get current value of RTC counter in microseconds
+ *
+ * Note: this function may take up to 1 RTC_SLOW_CLK cycle to execute
+ *
+ * @return current value of RTC counter in microseconds
+ */
+uint64_t esp_rtc_get_time_us(void);
+
+#ifdef __cplusplus
+}
+#endif