--- zzzz-none-000/linux-4.1.52/drivers/rtc/Kconfig	2018-05-28 02:26:45.000000000 +0000
+++ bcm63-7530ax-731/linux-4.1.52/drivers/rtc/Kconfig	2022-03-02 11:37:13.000000000 +0000
@@ -1555,5 +1555,11 @@
 	  If this driver is compiled as a module, it will be named
 	  rtc-hid-sensor-time.
 
+config RTC_DRV_AVM_REF_CLOCK
+    tristate "RTC Driver for external Clock source (DECT)"
+    depends on RTC_CLASS || AVM_DECT || ISDN_CAPI
+    default n
+    help
+        Clock source for Calibrate RTC device driver
 
 endif # RTC_CLASS