generic: mt7530: backport support for the MT7988 built-in switch

Backport commits adding support for the MT7988 built-in switch to the
mt7530 driver.

This change results in the Kconfig symbol NET_DSA_MT7530 to be extended
by NET_DSA_MT7530_MDIO (everything formally covered by NET_DSA_MT7530)
and NET_DSA_MT7530_MMIO (a new driver for the MMIO-connected built-in
switch of the MT7988 SoC).

Select NET_DSA_MT7530_MDIO for all targets previously selecting
NET_DSA_MT7530, with the exception of mediatek/filogic which also
selects NET_DSA_MT7530_MMIO.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(cherry picked from commit 958fdf36e35c814eb83faf2c39db4ca379c921b5)

1 files changed, 32 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.15/790-v6.4-0001-net-dsa-mt7530-make-some-noise-if-register-read-fail.patch b/target/linux/generic/backport-5.15/790-v6.4-0001-net-dsa-mt7530-make-some-noise-if-register-read-fail.patch
new file mode 100644
index 0000000000..ffbdde5a57
--- /dev/null
+++ b/target/linux/generic/backport-5.15/790-v6.4-0001-net-dsa-mt7530-make-some-noise-if-register-read-fail.patch
@@ -0,0 +1,32 @@
+From b6f56cddb5f57a0b8da0ce582232a2f1933558c6 Mon Sep 17 00:00:00 2001
+From: Daniel Golle <daniel@makrotopia.org>
+Date: Mon, 3 Apr 2023 02:17:19 +0100
+Subject: [PATCH 04/16] net: dsa: mt7530: make some noise if register read
+ fails
+
+Simply returning the negative error value instead of the read value
+doesn't seem like a good idea. Return 0 instead and add WARN_ON_ONCE(1)
+so this kind of error will not go unnoticed.
+
+Suggested-by: Andrew Lunn <andrew@lunn.ch>
+Signed-off-by: Daniel Golle <daniel@makrotopia.org>
+Reviewed-by: Andrew Lunn <andrew@lunn.ch>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ drivers/net/dsa/mt7530.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+--- a/drivers/net/dsa/mt7530.c
++++ b/drivers/net/dsa/mt7530.c
+@@ -224,9 +224,10 @@ mt7530_mii_read(struct mt7530_priv *priv
+ 	/* MT7530 uses 31 as the pseudo port */
+ 	ret = bus->write(bus, 0x1f, 0x1f, page);
+ 	if (ret < 0) {
++		WARN_ON_ONCE(1);
+ 		dev_err(&bus->dev,
+ 			"failed to read mt7530 register\n");
+-		return ret;
++		return 0;
+ 	}
+ 
+ 	lo = bus->read(bus, 0x1f, r);