Multistep hook_form_alter

I've been developing a module that alters the node edit form but requires to be multistep. Unfortunately, either the form executes the base node_form_submit OR my_form_alter_submit, but not both, causing that either the changes in my form alter don't appear or that the node is not saved and I'm taken back to the node edit form.

Can anyone point me in the right direction, maybe a module that does this right so I can take a hint?

The line that changes this behaviour is this: $form['#submit'][] = 'my_form_submit';