Security Random Number Generator support

[Neal Liu]

These patch series introduce a security random number generator
which provides a generic interface to get hardware rnd from Secure
state. The Secure state can be Arm Trusted Firmware(ATF), Trusted
Execution Environment(TEE), or even EL2 hypervisor.

Patch #1..2 adds sec-rng kernel driver for Trustzone based SoCs.
For security awareness SoCs on ARMv8 with TrustZone enabled,
peripherals like entropy sources is not accessible from normal world
(linux) and rather accessible from secure world (HYP/ATF/TEE) only.
This driver aims to provide a generic interface to Arm Trusted
Firmware or Hypervisor rng service.


changes since v1:
- rename mt67xx-rng to mtk-sec-rng since all MediaTek ARMv8 SoCs can reuse
  this driver.
  - refine coding style and unnecessary check.

  changes since v2:
  - remove unused comments.
  - remove redundant variable.

  changes since v3:
  - add dt-bindings for MediaTek rng with TrustZone enabled.
  - revise HWRNG SMC call fid.

  changes since v4:
  - move bindings to the arm/firmware directory.
  - revise driver init flow to check more property.

  changes since v5:
  - refactor to more generic security rng driver which
    is not platform specific.

*** BLURB HERE ***

Neal Liu (2):
  dt-bindings: rng: add bindings for sec-rng
  hwrng: add sec-rng driver

 .../devicetree/bindings/rng/sec-rng.yaml      |  53 ++++++
 drivers/char/hw_random/Kconfig                |  13 ++
 drivers/char/hw_random/Makefile               |   1 +
 drivers/char/hw_random/sec-rng.c              | 155 ++++++++++++++++++
 4 files changed, 222 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/rng/sec-rng.yaml
 create mode 100644 drivers/char/hw_random/sec-rng.c

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2.18.0