You work them out seperately. For Irish properties each profit/loss after allowable expenses is combined into an overall rental profit or loss, which is your total for Irish rental income on your tax return. For foreign properties, again each net figure is combined to give an overall total but is entered as foreign income on your return.
There is no need to submit each computation with the return but they must be kept along with receipts etc for deductions, in case of audit or even just verification checks that are sometimes when refunds are due.