code: void registerEntry(ListIterator<PathElement> iterator, ConcreteNotificationHandlerRegistration.NotificationHandlerEntry entry) {
          if (!iterator.hasNext()) {
              // leaf node, register the entry here
              entries.add(entry);
              return;
          }
          PathElement element = iterator.next();
          NotificationHandlerNodeSubregistry subregistry = getOrCreateSubregistry(element.getKey());
          subregistry.registerEntry(iterator, element.getValue(), entry);
      }
docs: Register the entry here (if the registry is the leaf node) or continue to traverse the tree