GmapJSONReader.php

class GmapJSONReader extends JSONReader {
  public function getSourceFields($url) {
    $items = parent::getSourceFields($url);
    // Loop over the JSON values, walk the tree and extract as keyed values.
    foreach ($items as &$item) {
      if (isset($item['address_components']) && is_array($item['address_components'])) {
        foreach ($item['address_components'] as $component) {
          if (isset($component['long_name']) && isset($component['types']) && is_array($component['types'])) {
            foreach ($component['types'] as $type) {
              $item[$type] = $component['long_name'];
            }
          }
        }
      }
      if (isset($item['geometry']['location']['lat'])) {
        $item['lat'] = $item['geometry']['location']['lat'];
      }
      if (isset($item['geometry']['location']['lng'])) {
        $item['lng'] = $item['geometry']['location']['lng'];
      }
    }

    return $items;
  }
}

GmapTypeJSONReader.php

class GmapTypeJSONReader extends JSONReader {
  public function getSourceFields($url) {
    $items = parent::getSourceFields($url);
    $return = [];
    // Loop over the JSON values and extract types
    // as individual rows.
    foreach ($items as &$item) {
      if (isset($item['types']) && is_array($item['types'])) {
        foreach ($item['types'] as $type)
        // We need to use place_id as the identifier for parsing JSON
        // in the parent class.
        // But we are really wanting to import an individual type
        // only once. So over-write the place_id with the type.
        $return[] = [
          'place_id' => $type,
          'type' => $type,
        ];

      }
    }

    return $return;
  }
}

migrate.migration.gmap.yml

id: gmap
migration_tags: JSON
label: gmap
source:
  plugin: json_source
  path: 'https://maps.googleapis.com/maps/api/geocode/json?latlng=40.714224,-73.961452'
  headers:
    Accept: application/json
  identifier: place_id
  identifierDepth: 1
  readerClass: Drupal\d8_json_migrate\Plugin\migrate\GmapJSONReader
  fields:
    - place_id
    - types
    - street_address
    - postal_code
    - country
    - locality
    - administrative_area_level_1
process:
  type:
    plugin: default_value
    default_value: gmaps
  title: country
  field_address_type:
    plugin: migration
    migration: gmap_type
    source: types
  field_city: locality
  field_country: country
  field_postal_code: postal_code
  field_state: administrative_area_level_1
  field_street_address: street_address
destination:
  plugin: 'entity:node'
template: null
migration_dependencies: {}
migration_group: JSON

migrate.migration.gmap_type.yml

id: gmap_type
migration_tags: JSON
label: 'gmap type'
source:
  plugin: json_source
  path: 'https://maps.googleapis.com/maps/api/geocode/json?latlng=40.714224,-73.961452'
  headers:
    Accept: application/json
  identifier: place_id
  identifierDepth: 1
  readerClass: Drupal\d8_json_migrate\Plugin\migrate\GmapTypeJSONReader
  fields:
    - type
process:
  name: type
  vid:
    plugin: default_value
    default_value: address_type
destination:
  plugin: 'entity:taxonomy_term'
template: null
migration_dependencies: {  }
migration_group: JSON