This PR support Nested interrupt in armv6/7/8m:
There are two types of nested interrupt model:
Zero latency nested interrupt
Interrupt Priority Note
Data abort Highest
SVC 0x50
High irq1 0x60 ISR can't access system API
irq_save() 0x70
High irq2 0x80 ISR can't access system API
normal irq3 0xB0
We have already support this mode before this PR
Nested interrupt which interrupt level lower than up_irq_save()
Interrupt Priority Note
Data abort Highest
SVC 0x70
irq_save() 0x80
High irq1 0x90 ISR can access system API
High irq2 0xA0 ISR can access system API
normal irq3 0xB0
Now, this PR can support this mode
Signed-off-by: ligd <liguiding1@xiaomi.com>