code: public void mergeSubsystem(final GlobalTransformerRegistry registry, String subsystemName, ModelVersion version) {
          final PathElement element = PathElement.pathElement(SUBSYSTEM, subsystemName);
          registry.mergeSubtree(this, PathAddress.EMPTY_ADDRESS.append(element), version);
      }
docs: Merge a new subsystem from the global registration.
  
  @param registry the global registry
  @param subsystemName the subsystem name
  @param version the subsystem version