[RFC net-next 1/3] dt-bindings: net: airoha: npu: add DMA pool memory region

[Chris Scott <gilroyscott1970@gmail.com>]

From: Daniel Pawlik <pawlik.dan@gmail.com>

The EN7581 NPU can only address host DRAM at 0x80000000-0xbfffffff;
higher addresses alias the lower 1 GiB. Allow an optional shared DMA
pool, after the firmware region or after the WLAN regions, so coherent
buffers shared with the NPU can be kept inside that window. The
firmware region stays first for existing users.

The original version of this patch was written with Codex; it was
rebased onto net-next and its commit message rewritten with Claude
(Anthropic).

Link: https://lore.kernel.org/r/atCRsquzA1UxSpCc@mediatek.com
Signed-off-by: Daniel Pawlik <pawlik.dan@gmail.com>
Signed-off-by: Chris Scott <gilroyscott1970@gmail.com>
---
 .../bindings/net/airoha,en7581-npu.yaml       | 40 ++++++++++++-------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/airoha,en7581-npu.yaml b/Documentation/devicetree/bindings/net/airoha,en7581-npu.yaml
index aefa19c5b4..21a1a27500 100644
--- a/Documentation/devicetree/bindings/net/airoha,en7581-npu.yaml
+++ b/Documentation/devicetree/bindings/net/airoha,en7581-npu.yaml
@@ -42,22 +42,34 @@ properties:
       - description: wlan irq line5
 
   memory-region:
-    items:
-      - description: NPU firmware binary region
-      - description: NPU wlan offload RX buffers region
-      - description: NPU wlan offload TX buffers region
-      - description: NPU wlan offload TX packet identifiers region
-      - description: NPU wlan Block Ack buffers region
-    minItems: 1
+    oneOf:
+      - items:
+          - description: NPU firmware binary region
+          - description: Coherent DMA pool for buffers shared with the NPU
+        minItems: 1
+      - items:
+          - description: NPU firmware binary region
+          - description: NPU wlan offload RX buffers region
+          - description: NPU wlan offload TX buffers region
+          - description: NPU wlan offload TX packet identifiers region
+          - description: NPU wlan Block Ack buffers region
+          - description: Coherent DMA pool for buffers shared with the NPU
+        minItems: 4
 
   memory-region-names:
-    items:
-      - const: firmware
-      - const: pkt
-      - const: tx-pkt
-      - const: tx-bufid
-      - const: ba
-    minItems: 1
+    oneOf:
+      - items:
+          - const: firmware
+          - const: dma
+        minItems: 1
+      - items:
+          - const: firmware
+          - const: pkt
+          - const: tx-pkt
+          - const: tx-bufid
+          - const: ba
+          - const: dma
+        minItems: 4
 
   firmware-name:
     items:
-- 
2.53.0