rtc: add function to en/disable the rtc clock

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

@@ -459,6 +459,29 @@ uint64_t rtc_time_get(void);
  */
 void rtc_clk_wait_for_slow_cycle(void);
 
+/**
+ * @brief Enable the rtc digital 8M clock
+ *
+ * This function is used to enable the digital rtc 8M clock to support peripherals.
+ * For enabling the analog 8M clock, using `rtc_clk_8M_enable` function above.
+ */
+void rtc_dig_clk8m_enable(void);
+
+/**
+ * @brief Disable the rtc digital 8M clock
+ *
+ * This function is used to disable the digital rtc 8M clock, which is only used to support peripherals.
+ */
+void rtc_dig_clk8m_disable(void);
+
+/**
+ * @brief Caculate the real clock value after the clock calibration
+ *
+ * @param cal_val average slow clock period in microseconds, can be return from `rtc_clk_cal`
+ * @return The real value of the clock has been measured
+ */
+uint32_t rtc_clk_freq_cal(uint32_t cal_val);
+
 /**
  * @brief sleep configuration for rtc_sleep_init function
  */