[U-Boot] [PATCH v4 3/4] doc: dtbinding: add pwm binding file

[sjg at google.com]

This is a copy from kernel.

Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
Acked-by: Simon Glass <sjg at chromium.org>
---

Changes in v4: None
Changes in v3: None
Changes in v2: None

 doc/device-tree-bindings/pwm/pwm.txt | 69 ++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 doc/device-tree-bindings/pwm/pwm.txt

Applied to u-boot-rockchip/next, thanks!