CustomNodeDefinition example

->arrayNode('pipou')
                    ->useAttributeAsKey('name')
                    ->prototype('array')
                        ->prototype('array')
                            ->children()
                                ->scalarNode('didou')
                                ->end()
                            ->end()
                        ->end()
                    ->end()
                ->end()
                ->append(new CustomNodeDefinition('acme'))
            ->end()
        ;

        return $treeBuilder;
    }
}