Issue #3199587 by DamienMcKenna: Migrate support to upgrade EXIF field formatters from D7 to D8.

src/Plugin/migrate/field/d7/ExifReadOnly.php

+<?php
+
+namespace Drupal\exif\Plugin\migrate\field\d7;
+
+use Drupal\migrate_drupal\Plugin\migrate\field\FieldPluginBase;
+
+/**
+ * @MigrateField(
+ *   id = "exif_read_only",
+ *   core = {7},
+ *   source_module = "exif",
+ *   destination_module = "exif"
+ * )
+ */
+class ExifReadOnly extends FieldPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFieldWidgetMap() {
+    return [
+      'exif_readonly' => 'exif_readonly',
+    ];
+  }
+
+}