user_role_grant_permissions

user_role_grant_permissions($rid, array $permissions = array())

function user_role_grant_permissions($rid, array $permissions = array()) {
  // Grant new permissions for the role.
  if ($role = Role::load($rid)) {
    foreach ($permissions as $permission) {
      $role->grantPermission($permission);
    }
    $role->trustData()->save();
  }
}