code: private static IIOMetadataNode getOrCreateChildNode(IIOMetadataNode parentNode, String name)
      {
          NodeList nodeList = parentNode.getElementsByTagName(name);
          if (nodeList.getLength() > 0)
          {
              return (IIOMetadataNode) nodeList.item(0);
          }
          IIOMetadataNode childNode = new IIOMetadataNode(name);
          parentNode.appendChild(childNode);
          return childNode;
      }
docs: Gets the named child node, or creates and attaches it.
  
  @param parentNode the parent node
  @param name name of the child node
  
  @return the existing or just created child node