code: public ModelNode getDeploymentSubsystemModel(final String subsystemName) {
          assert subsystemName != null : "The subsystemName cannot be null";
          return getDeploymentSubModel(subsystemName, PathAddress.EMPTY_ADDRESS, null, deploymentUnit);
      }
docs: Get the subsystem deployment model root.
  
  <p>
  If the subsystem resource does not exist one will be created.
  </p>
  
  @param subsystemName the subsystem name.
  
  @return the model