Retrieval architecture diagram?

[Clint Byrum]

There is much talk about how MySQL Cluster stores data, but I can't seem
to find a definitive answer as to how it retrieves data.

My thought was that it would submit the query to each node-group, do
processing there, and then the API must collate/join the results from
each node group. That, or the node groups somehow work together to join
their result sets.

Is this far off the mark? Is there a diagram somewhere I can look at?

Thanks!