doc: doxygen: add missing groups and categorise

Add various missing groups and categorise modules correctly.

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

include/canbus/canopen.h

@@ -4,6 +4,13 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+
+/**
+ * @defgroup CAN CAN BUS
+ * @{
+ * @}
+ */
+
 /**
  * @brief CANopen Network Stack
  * @defgroup canopen CANopen Network Stack

include/random/rand32.h

@@ -26,6 +26,7 @@
 /**
  * @brief Random Function APIs
  * @defgroup random_api Random Function APIs
+ * @ingroup crypto
  * @{
  */
 

include/settings/settings.h

@@ -17,8 +17,15 @@
 extern "C" {
 #endif
 
+
 /**
- * @defgroup settings Settings subsystem
+ * @defgroup file_system_storage File System Storage
+ * @{
+ * @}
+ */
+
+/**
+ * @defgroup settings Settings
  * @ingroup file_system_storage
  * @{
  */
@@ -351,7 +358,7 @@ int settings_commit_subtree(const char *subtree);
 
 /**
  * @defgroup settings_backend Settings backend interface
- * @ingroup file_system_storage
+ * @ingroup settings
  * @{
  */