Docs: Fixes link to I2C specification

The link to the I2C specification is broken. Although
"https://www.nxp.com" hosts Rev 7 (2021) of this specification, it is
behind a login-wall. Thus, an additional link has been added (which
doesn't require a login) and the NXP official docs link has been
updated.

Signed-off-by: Deep Majumder <deep@fastmail.in>
[wsa: minor updates to text and commit message]
Signed-off-by: Wolfram Sang <wsa@kernel.org>
This commit is contained in:
Deep Majumder 2021-11-19 11:44:01 +05:30 committed by Wolfram Sang
parent bb436283e2
commit c116fe1e18
1 changed files with 5 additions and 3 deletions

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@ -11,9 +11,11 @@ systems. Some systems use variants that don't meet branding requirements,
and so are not advertised as being I2C but come under different names,
e.g. TWI (Two Wire Interface), IIC.
The official I2C specification is the `"I2C-bus specification and user
manual" (UM10204) <https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_
published by NXP Semiconductors.
The latest official I2C specification is the `"I2C-bus specification and user
manual" (UM10204) <https://www.nxp.com/webapp/Download?colCode=UM10204>`_
published by NXP Semiconductors. However, you need to log-in to the site to
access the PDF. An older version of the specification (revision 6) is archived
`here <https://web.archive.org/web/20210813122132/https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_.
SMBus (System Management Bus) is based on the I2C protocol, and is mostly
a subset of I2C protocols and signaling. Many I2C devices will work on an