try to fetch needed mcu submodule while running make

examples/make.mk

@@ -15,20 +15,8 @@ check_defined = \
 __check_defined = \
     $(if $(value $1),, \
     $(error Undefined make flag: $1$(if $2, ($2))))
-    
-# TODO Check if submodule haven't checkout yet
-fetch_submodule_if_empty = \
-  ifeq ($(wildcard $(TOP)/$1/*),) \
-    $(info $(shell git -C $(TOP) submodule update --init)) \
-  endif
 
 #-------------- Select the board to build for. ------------
-#BOARD_LIST = $(sort $(subst /.,,$(subst $(TOP)/hw/bsp/,,$(wildcard $(TOP)/hw/bsp/*/.))))
-#ifeq ($(filter $(BOARD),$(BOARD_LIST)),)
-#  $(info You must provide a BOARD parameter with 'BOARD=', supported boards are:)
-#  $(foreach b,$(BOARD_LIST),$(info - $(b)))
-#  $(error Invalid BOARD specified)
-#endif
 
 # Board without family
 BOARD_PATH := $(subst $(TOP)/,,$(wildcard $(TOP)/hw/bsp/$(BOARD)))
@@ -42,6 +30,7 @@ ifeq ($(BOARD_PATH),)
 endif
 
 ifeq ($(BOARD_PATH),)
+  $(info You must provide a BOARD parameter with 'BOARD=')
   $(error Invalid BOARD specified)
 endif
 
@@ -56,6 +45,16 @@ endif
 
 #TODO $(call fetch_submodule_if_empty,lib/sct_neopixel)
 
+# Fetch submodules depended by family
+fetch_submodule_if_empty = \
+  ifeq ($(wildcard $(TOP)/$1/*),) \
+    $(info $(shell git -C $(TOP) submodule update --init $1)) \
+  endif
+
+ifdef FAMILY_SUBMODULES
+  $(foreach s,$(FAMILY_SUBMODULES),:$(call fetch_submodule_if_empty,$(s)))
+endif
+
 #-------------- Cross Compiler  ------------
 # Can be set by board, default to ARM GCC
 CROSS_COMPILE ?= arm-none-eabi-