add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/Documentation/ABI/testing/sysfs-bus-platform
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@@ -18,3 +18,13 @@
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 		devices to opt-out of driver binding using a driver_override
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 		name such as "none".  Only a single driver may be specified in
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 		the override, there is no support for parsing delimiters.
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+
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+What:		/sys/bus/platform/devices/.../numa_node
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+Date:		June 2020
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+Contact:	Barry Song <song.bao.hua@hisilicon.com>
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+Description:
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+		This file contains the NUMA node to which the platform device
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+		is attached. It won't be visible if the node is unknown. The
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+		value comes from an ACPI _PXM method or a similar firmware
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+		source. Initial users for this file would be devices like
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+		arm smmu which are populated by arm64 acpi_iort.