Polled interrupts: how does the CPU know which ISR to run?

Hello, may someone help me to understand this?
I know that in vectored interrupts, a device asks the CPU to run a certain ISR by sending a specific code. Now, in polled interrupts there's no interrupt vector. So how does the CPU know what's the Interrupt Service Routine to be run?
Perhaps there's only one Interrupt Service Routine per device? Or maybe each device can request one Routine per Interrupt Priority Level, so that the CPU knows what to do just by recognizing the device and the Priority Level of the request?

Thanks a lot for your help.
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More about polled interrupts
  1. Nutshell: Polled interrupts aren't a general mechanism like incoming interrupts from devices. Instead, the CPU, or rather the device driver that's doing the polling, knows where to look and what it's waiting for.
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