/media/test/tmpUpload

location ~ ^/(app|app_dev|config).php(/|$) {
    #other parameters
    fastcgi_pass unix:/var/run/php72-fpm.sock;
    fastcgi_split_path_info ^(.+.php)(/.*)$;
    include fastcgi_params;
    fastcgi_param  SCRIPT_FILENAME $document_root$fastcgi_script_name;
    fastcgi_param   SERVER_NAME         $host;
    fastcgi_param PHP_VALUE "short_open_tag=Off

    post_max_size = 400M
    upload_max_filesize = 400M
    upload_tmp_dir = /media/test/tmpUpload
    ";
}

echo ini_get('upload_tmp_dir');

var_dump($_FILES['file']);

/media/test/tmpUpload

array(5)
{
  ["name"]=>
  string(51) "xxxxxxxxxxxxxxxx.pdf"
  ["type"]=>
  string(15) "application/pdf"
  ["tmp_name"]=>
  string(14) "/tmp/phpe2mutM"
  ["error"]=>
  int(0)
  ["size"]=>
  int(774476)
}