Need clarity on MSI handling in RC driver

[valmiki]

Hi All,

I have a doubt, the MSI domains are handled differently in different RC 
drivers.

Some drivers use irq_domain_add_linear alone, and some use 
pci_msi_create_irq_domain also to handle MSI.

In most of the 32-bit architectures only irq_domain_add_linear is used 
and in 64 bit drivers both pci_msi_create_irq_domain and 
irq_domain_add_linear are used.

So is this because of architecture difference between ARM and ARM64 ?

Thanks & Regards,
valmiki