dt-bindings: net: dsa: mediatek,mt7530: update binding description

Update the description of the binding.

- Describe the switches, which SoCs they are in, or if they are standalone.
- Explain the various ways of configuring MT7530's port 5.
- Remove phy-mode = "rgmii-txid" from description. Same code path is
followed for delayed rgmii and rgmii phy-mode on mtk_eth_soc.c.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/dsa/mediatek,mt7530.yaml

@@ -13,41 +13,68 @@ maintainers:
   - Sean Wang <sean.wang@mediatek.com>
 
 description: |
-  Port 5 of mt7530 and mt7621 switch is muxed between:
-  1. GMAC5: GMAC5 can interface with another external MAC or PHY.
-  2. PHY of port 0 or port 4: PHY interfaces with an external MAC like 2nd GMAC
-     of the SOC. Used in many setups where port 0/4 becomes the WAN port.
-     Note: On a MT7621 SOC with integrated switch: 2nd GMAC can only connected to
-       GMAC5 when the gpios for RGMII2 (GPIO 22-33) are not used and not
-       connected to external component!
+  There are two versions of MT7530, standalone and in a multi-chip module.
 
-  Port 5 modes/configurations:
-  1. Port 5 is disabled and isolated: An external phy can interface to the 2nd
-     GMAC of the SOC.
-     In the case of a build-in MT7530 switch, port 5 shares the RGMII bus with 2nd
-     GMAC and an optional external phy. Mind the GPIO/pinctl settings of the SOC!
-  2. Port 5 is muxed to PHY of port 0/4: Port 0/4 interfaces with 2nd GMAC.
-     It is a simple MAC to PHY interface, port 5 needs to be setup for xMII mode
-     and RGMII delay.
-  3. Port 5 is muxed to GMAC5 and can interface to an external phy.
-     Port 5 becomes an extra switch port.
-     Only works on platform where external phy TX<->RX lines are swapped.
-     Like in the Ubiquiti ER-X-SFP.
-  4. Port 5 is muxed to GMAC5 and interfaces with the 2nd GAMC as 2nd CPU port.
-     Currently a 2nd CPU port is not supported by DSA code.
+  MT7530 is a part of the multi-chip module in MT7620AN, MT7620DA, MT7620DAN,
+  MT7620NN, MT7621AT, MT7621DAT, MT7621ST and MT7623AI SoCs.
 
-  Depending on how the external PHY is wired:
-  1. normal: The PHY can only connect to 2nd GMAC but not to the switch
-  2. swapped: RGMII TX, RX are swapped; external phy interface with the switch as
-     a ethernet port. But can't interface to the 2nd GMAC.
+  MT7530 in MT7620AN, MT7620DA, MT7620DAN and MT7620NN SoCs has got 10/100 PHYs
+  and the switch registers are directly mapped into SoC's memory map rather than
+  using MDIO. The DSA driver currently doesn't support this.
 
-    Based on the DT the port 5 mode is configured.
+  There is only the standalone version of MT7531.
 
-  Driver tries to lookup the phy-handle of the 2nd GMAC of the master device.
-  When phy-handle matches PHY of port 0 or 4 then port 5 set-up as mode 2.
-  phy-mode must be set, see also example 2 below!
-  * mt7621: phy-mode = "rgmii-txid";
-  * mt7623: phy-mode = "rgmii";
+  Port 5 on MT7530 has got various ways of configuration.
+
+  For standalone MT7530:
+
+    - Port 5 can be used as a CPU port.
+
+    - PHY 0 or 4 of the switch can be muxed to connect to the gmac of the SoC
+      which port 5 is wired to. Usually used for connecting the wan port
+      directly to the CPU to achieve 2 Gbps routing in total.
+
+      The driver looks up the reg on the ethernet-phy node which the phy-handle
+      property refers to on the gmac node to mux the specified phy.
+
+      The driver requires the gmac of the SoC to have "mediatek,eth-mac" as the
+      compatible string and the reg must be 1. So, for now, only gmac1 of an
+      MediaTek SoC can benefit this. Banana Pi BPI-R2 suits this.
+      Check out example 5 for a similar configuration.
+
+    - Port 5 can be wired to an external phy. Port 5 becomes a DSA slave.
+      Check out example 7 for a similar configuration.
+
+  For multi-chip module MT7530:
+
+    - Port 5 can be used as a CPU port.
+
+    - PHY 0 or 4 of the switch can be muxed to connect to gmac1 of the SoC.
+      Usually used for connecting the wan port directly to the CPU to achieve 2
+      Gbps routing in total.
+
+      The driver looks up the reg on the ethernet-phy node which the phy-handle
+      property refers to on the gmac node to mux the specified phy.
+
+      For the MT7621 SoCs, rgmii2 group must be claimed with rgmii2 function.
+      Check out example 5.
+
+    - In case of an external phy wired to gmac1 of the SoC, port 5 must not be
+      enabled.
+
+      In case of muxing PHY 0 or 4, the external phy must not be enabled.
+
+      For the MT7621 SoCs, rgmii2 group must be claimed with rgmii2 function.
+      Check out example 6.
+
+    - Port 5 can be muxed to an external phy. Port 5 becomes a DSA slave.
+      The external phy must be wired TX to TX to gmac1 of the SoC for this to
+      work. Ubiquiti EdgeRouter X SFP is wired this way.
+
+      Muxing PHY 0 or 4 won't work when the external phy is connected TX to TX.
+
+      For the MT7621 SoCs, rgmii2 group must be claimed with gpio function.
+      Check out example 7.
 
 properties:
   compatible: