This code system http://hl7.org/fhir/fundsreserve defines the following codes:

CodeDisplayDefinition
patientPatientThe payor is requested to reserve funds for the provision of the named services by any provider for settlement of future claims related to this request.
providerProviderThe payor is requested to reserve funds solely for the named provider for settlement of future claims related to this request.
noneNoneThe payor is not being requested to reserve any funds for the settlement of future claims.