Laravel: query builder with relationship

I have a table with input fields that act as filters. There are values from Orders table and Users table which has a relationship.

e.g.:

Order Id     | User Full Name   | Order Price | Date              |

[order filter] [user name filter]               [order date filter]

How can I filter a value from a users table via relationship?

This returns error of course:

public function name($name)
{
    return $this->builder->where('name', 'LIKE', '%$name%')->orWhere('surname', 'LIKE', '%$name%');
}

Error:

QueryException in Connection.php line 770:
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'name' in 'where clause' (SQL: select count(*) as aggregate from `orders` where (`name` LIKE %$name% or `surname` LIKE %$name%))

via Rudolph