How to attach Dropzone.js uploads to a form element
I now have the files under $_FILES['files'].

My JS code:

(function ($) {

    Drupal.behaviors.dz = {
        attach: function (context, settings) {
            Dropzone.options.picsForm = {
                paramName: "files",
                autoProcessQueue: false,
                uploadMultiple: true,
                parallelUploads: 100,
                maxFiles: 100,

                init: function() {
                    var dz = this;
                    // #edit-next is the id of my submit button
                    this.element.querySelector("#edit-next").addEventListener("click", function(e) {
                        e.preventDefault();
                        e.stopPropagation();
                        dz.processQueue();
                    });

                }
            };

        }
      }

})(jQuery);


The '$form_field_name' parameter is a numeric index now, so I just get the count of the $_FILES['names'] array and call file_save_upload() for each one.