Add Samsung Exynos true random number generator driver

[m-falkowski1]

Hello,

As a part of the introduction of our kernel team to the RustForLinux project,
I created a driver that is a port of Samsung Exynos true random number generator that now I would like to present.

This is mainly a request for an initial code review. There are some patches that are not yet prepared and require some design decisions. The power management of the driver is for now skipped as it was not needed to get the driver working.

The driver is tested on the ODROID-XU3 board (Exynos 5422).

---

• rust: drivers: char: hw_random: add Exynos HWRNG driver
• rust: iopoll: add read_poll_timeout function #701
• rust: ktime: add ktime_get, ktime_add_us, ktime_compare bindings
• rust: delay: add usleep_range function
• rust: add pm_runtime bindings #700
• rust: platform: add ioremap_resource and get_resource methods #682
• rust: iomem: add try_memcpy_fromio method for IoMem<T> #681
• rust: iomem: add readx/writex relaxed family of functions #621
• rust: add initial common clock framework bindings #593
• rust: add Hardware Random Number Generator subsystem #592

[ojeda]

A few random comments (pun not intended :)

[m-falkowski1]

@ojeda May I ask Miguel, the first patches of the patchset have been significantly improved, thus I think I could start submitting them one by one in separates pull requests. The last patches related to io_mem and iopoll are still much in progress so maybe it would be better to await them?

What would you prefer?
Best regards

[ojeda]

Yeah, please feel free to split the PR into several. The smaller they are, the easier they are to take (as long as commits are consistent, i.e. that they do not break the build).