DRA: Partitionable Devices: Add Overview

Signed-off-by: Kevin Klues <[email protected]>

keps/sig-node/4815-dra-partitionable-devices/README.md

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+One of the original use-cases for Dynamic Resource Allocation (DRA) was the
+ability to dynamically allocate "partitions" of a full device (in addition to
+the full device itself). While the traditional device plugin API forces users
+to statically partition devices ahead of time, DRA was designed to allow those
+partitions to be created on demand. This, in turn, leads to increased resource
+utilization as the size of each partitioned device can be matched in real-time
+to the workload requesting it.
+
+As DRA has evolved from what we now call "classic" DRA to "structured
+parameters" this ability to dynamically partition devices has been lost.
+This KEP proposes a method to bring this capability back within the framework
+that "structured parameters" provides.
 
 ## Motivation