If I have an address (pointer) in virtual addressing area of current process to the pinned (page-locked) memory, then how can I get an address (pointer) in physical addressing area, of this memory region, by using POSIX?
You cannot access physical addresses in user space. Everything you do goes through the MMU and the page tables. Even if you pin a page, the kernel may still move it around in physical memory.
Even if you got it, what would it do for you? A userspace process cannot access memory directly by physical access. Only kernel mode can.
If you really need the functionality (although I still can't image any way of using the information), you have to write a kernel mode driver.