Add support for STM32F098xx SOC and Google Kukui reference board

[jackrosenthal]

This adds support for the EC (embedded controller) on a Google reference board with codename "kukui". This board uses the STM32F098RC chip. We built an application for the board and verified UART functionality on the board.

[ulfalizer]

Some nits related to some recent cleanups.

[zephyrbot]

All checks are passing now.

checkpatch (informational only, not a failure)

-:175: WARNING:UNDOCUMENTED_DT_STRING: DT compatible string "st,stm32f098rc" appears un-documented -- check ./dts/bindings/
#175: FILE: boards/arm/google_kukui/google_kukui.dts:12:
+	compatible = "st,stm32f098rc", "st,stm32f098";

-:175: WARNING:UNDOCUMENTED_DT_STRING: DT compatible string "st,stm32f098" appears un-documented -- check ./dts/bindings/
#175: FILE: boards/arm/google_kukui/google_kukui.dts:12:
+	compatible = "st,stm32f098rc", "st,stm32f098";

- total: 0 errors, 2 warnings, 284 lines checked

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NOTE: Ignored message types: AVOID_EXTERNS BRACES CONFIG_EXPERIMENTAL CONST_STRUCT DATE_TIME FILE_PATH_CHANGES MINMAX NETWORKING_BLOCK_COMMENT_STYLE PRINTK_WITHOUT_KERN_LEVEL SPLIT_STRING VOLATILE

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[ulfalizer]

-:80: WARNING:UNDOCUMENTED_DT_STRING: DT compatible string "st,stm32f098rc" appears un-documented -- check ./dts/bindings/
#80: FILE: boards/arm/google_kukui/google_kukui.dts:12:

• compatible = "st,stm32f098rc", "st,stm32f098";

#20289 would've helped here, but it doesn't seem to be in yet.

[jackrosenthal]

-:80: WARNING:UNDOCUMENTED_DT_STRING: DT compatible string "st,stm32f098rc" appears un-documented -- check ./dts/bindings/
#80: FILE: boards/arm/google_kukui/google_kukui.dts:12:

• compatible = "st,stm32f098rc", "st,stm32f098";

#20289 would've helped here, but it doesn't seem to be in yet.

Should I do anything to resolve this warning, or leave as is?

[ulfalizer]

Should I do anything to resolve this warning, or leave as is?

Could leave as is.

Another option would be to mention those compatibles in a comment in a binding just to make the check happy (checkpatch.pl is just grepping for the strings internally), and use variant-compatible later if we remember.

Not super important at least.

[ulfalizer]

Nits fixed.

[erwango]

Thanks for this addition!
Additionally to the comments on the files, please take care to the 3 following points:

• Please add board documentation
• Please rename first commit to soc: ... since you're actually touching soc sbsystem, not dt
• Please add a dts related to cmmit to add the missing soc dtsi files

[jackrosenthal]

Thanks for this addition!
Additionally to the comments on the files, please take care to the 3 following points:

• Please add board documentation

Done. Apologies that the documentation may be a little slim, the board is not released yet and I'm not able to provide photos, etc.

• Please rename first commit to soc: ... since you're actually touching soc sbsystem, not dt

Done

• Please add a dts related to cmmit to add the missing soc dtsi files

Done. It's equivalent to STM32F091xC, but I copied the files.

[erwango]

Some more comments.
Also, please add yourself in front of this board in CODEOWNER file

[erwango]

One remaining comment on .dtsi package variant file name.
Otherwise this is fine.

[jackrosenthal]

What steps remain in getting this merged?

[erwango]

@jackrosenthal, we're in the process of releasing v2.1, so merge window is frozen for now. New one should be open in a couple of weeks.

[dbkinder]

+1 for docs, thanks.