A taxing authority of a subdivision may establish a nonexpendable trust fund for the purpose of receiving donations or contributions that the donor or contributor requires to be maintained intact. The principal of such fund may be invested, and the investment earnings on the principal shall be credited to the fund. The principal of the fund, and any additions to principal arising from sources other than the reinvestment of investment earnings arising from the fund, shall not be considered part of the unencumbered balance or revenue of the subdivision under division (A) of section 5705.35 or division (A)(1) of section 5705.36 of the Revised Code. Only investment earnings arising from investment of the principal or investment of such additions to principal may be considered an unencumbered balance or revenue of the subdivision under that division.