init: enhance kconfig docs for custom hooks

Improve docs for custom soc/board hooks.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

kernel/Kconfig.init

@@ -27,19 +27,31 @@ config SOC_EARLY_INIT_HOOK
 	help
 	  Run an early SoC initialization hook.
 
+	  A custom SoC hook soc_early_init_hook() is executed before the kernel and
+	  devices are initialized
+
 config SOC_LATE_INIT_HOOK
 	bool "Run late SoC hook"
 	help
 	  Run a late SoC initialization hook.
 
+	  A custom SoC hook soc_late_init_hook() is executed after the kernel and
+	  devices are initialized
+
 config BOARD_EARLY_INIT_HOOK
 	bool "Run early board hook"
 	help
 	  Run an early board initialization hook.
 
+	  A custom board hook board_early_init_hook() is executed before the kernel and
+	  devices are initialized
+
 config BOARD_LATE_INIT_HOOK
 	bool "Run late board hook"
 	help
 	  Run a late board initialization hook.
 
+	  A custom board hook board_late_init_hook() is executed after the kernel and
+	  devices are initialized
+
 endmenu