question about soft irq

["dyd" <dyd@process.buaa.edu.cn>]

Hi, all

We know that the way using soft irq in rtl is first
    rtl_get_soft_irq(linux_handler,name)

>From the code I know that when /rtl_get_soft_irq/, it will occupy one item
of /irq_desc/
and assign it the corresponding handler, etc.

My question is : Why we use /irq_desc/? After all, it is a precious resource
shared by
hardware interrupt. We can use another array to record soft-irq, And check
the array
when /rtl_intercept/.

If there any are other reasons than just save some labor? Or I make some
mistake?

Thanks a lot.

Regards
Du Yuedong