realtek: pcs: add SerDes page definitions

To reduce having magic values all over the place in the whole driver,
add definitions for the SerDes register pages. They are equal among all
variants and can be clearly named, as already done in the debugfs output
of the realtek-otto-serdes-mdio driver. This should ease comparison,
code understanding and very likely is a step forward towards
upstream-readyness.

Also define two macros to cover the special cases for RTL931x's digital
SerDes via 0x40/0x80 page offset.

Link: https://github.com/openwrt/openwrt/pull/23915
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>

target/linux/realtek/files-6.18/drivers/net/pcs/pcs-rtl-otto.c

@@ -116,6 +116,56 @@
 #define RTPCS_931X_SDS_MAIN_AMP_MASK		GENMASK(9, 5)
 #define RTPCS_931X_SDS_POST_AMP_MASK		GENMASK(14, 10)
 
+/*
+ * A SerDes has a register space separated into several pages. Each page
+ * serves a different purpose and is the home of common settings. E.g.,
+ * there are dedicated pages for each operating speed of a SerDes.
+ */
+enum rtpcs_page {
+	PAGE_SDS		= 0x00,
+	PAGE_SDS_EXT		= 0x01,
+	PAGE_FIB		= 0x02,
+	PAGE_FIB_EXT		= 0x03,
+	PAGE_TGR_STD_0		= 0x04,
+	PAGE_TGR_STD_1		= 0x05,
+	PAGE_TGR_PRO_0		= 0x06,
+	PAGE_TGR_PRO_1		= 0x07,
+	PAGE_TGX_STD_0		= 0x08,
+	PAGE_TGX_STD_1		= 0x09,
+	PAGE_TGX_PRO_0		= 0x0a,
+	PAGE_TGX_PRO_1		= 0x0b,
+	PAGE_WDIG		= 0x1f,
+	PAGE_ANA_MISC		= 0x20,
+	PAGE_ANA_COM		= 0x21,
+	PAGE_ANA_SPD		= 0x22,
+	PAGE_ANA_SPD_EXT	= 0x23,
+	PAGE_ANA_1G2		= 0x24,
+	PAGE_ANA_1G2_EXT	= 0x25,
+	PAGE_ANA_2G5		= 0x26,
+	PAGE_ANA_2G5_EXT	= 0x27,
+	PAGE_ANA_3G1		= 0x28,
+	PAGE_ANA_3G1_EXT	= 0x29,
+	PAGE_ANA_5G0		= 0x2a,
+	PAGE_ANA_5G0_EXT	= 0x2b,
+	PAGE_ANA_6G2		= 0x2c,
+	PAGE_ANA_6G2_EXT	= 0x2d,
+	PAGE_ANA_10G		= 0x2e,
+	PAGE_ANA_10G_EXT	= 0x2f,
+	PAGE_GPON_SP		= 0x30,
+	PAGE_GPON_SP_EXT	= 0x31,
+	PAGE_EPON_SP		= 0x32,
+	PAGE_EPON_SP_EXT	= 0x33,
+	PAGE_ANA_6G0		= 0x34,
+	PAGE_ANA_6G0_EXT	= 0x35,
+};
+
+/*
+ * RTL931X only: the digital SDS 1/2 register pages mirror an analog page at a
+ * fixed +0x40 / +0x80 region offset. See rtpcs_931x_sds_op_xsg_write().
+ */
+#define DIGI_1(page)	((page) + 0x40)
+#define DIGI_2(page)	((page) + 0x80)
+
 enum rtpcs_sds_type {
 	RTPCS_SDS_TYPE_UNKNOWN,
 	RTPCS_SDS_TYPE_5G,