RouteSubscriber.php

<?php

namespace Drupal\node\Routing;

use Drupal\Core\Routing\RouteSubscriberBase;
use Symfony\Component\Routing\RouteCollection;

/**
 * Listens to the dynamic route events.
 */
class RouteSubscriber extends RouteSubscriberBase {

  /**
   * {@inheritdoc}
   */
  protected function alterRoutes(RouteCollection $collection) {

    // As nodes are the primary type of content, the node listing should be
    // easily available. In order to do that, override admin/content to show
    // a node listing instead of the path's child links.
    $route = $collection
      ->get('system.admin_content');
    if ($route) {
      $route
        ->setDefaults([
        '_title' => 'Content',
        '_entity_list' => 'node',
      ]);
      $route
        ->setRequirements([
        '_permission' => 'access content overview',
      ]);
    }
  }

}