Complete the architecture specification for an advanced interrupt controller with full virtualization support

Development of a next generation interrupt architecture suitable for Linux-class (aka Rich OS) systems as will be standardized by the OS/A Platform Spec, which includes the following capabilities:

• Scalable from large-scale feature-rich systems down to smaller, simpler systems
• Efficient support for both wired interrupts and message-based interrupts (including PCIe MSI/MSI-X's)
• Virtualization support
  • Works effectively with CPU virtualization (i.e. the Hypervisor Extension)
  • Scalable to handling large numbers of active VMs
  • Interrupt virtualization
  • Direct I/O device control by guest OSs
  • Direct injection of virtual interrupts into VMs
• Build upon the interrupt handling functionality in the current Privileged Architecture and minimize the replacement of existing functionality
• Additional standardized hart-local interrupts (such as for debug/trace and RAS)