--- zzzz-none-000/linux-4.9.231/drivers/isdn/hardware/avm/Kconfig	2020-07-22 07:10:54.000000000 +0000
+++ falcon-5590-729/linux-4.9.231/drivers/isdn/hardware/avm/Kconfig	2022-03-30 12:03:34.000000000 +0000
@@ -61,4 +61,6 @@
 	  Enable support for the AVM C4/C2 PCI cards.
 	  These cards handle 4/2 BRI ISDN lines (8/4 channels).
 
+source "drivers/isdn/isdn_fon5/Kconfig"
+
 endif # CAPI_AVM