An assignment of a mortgage may be recorded or filed in the same manner as a mortgage, and the record thereof operates as notice to all persons subsequently deriving title to the mortgage from the assignor. When the mortgage is executed as security for money due or to become due on a promissory note, bond, or other instrument designated in the mortgage, the record of the assignment of the mortgage is not of itself notice to a mortgagor or a mortgagor’s heirs or personal representatives so as to invalidate any payment made by them or either of them to the person holding such note, bond, or other instrument.