Add support for FOXNEO FNS-1200P (RTL8372, 4x2.5G PoE+ + 2x SFP+)

- machine.c/h: add MACHINE_FNS1200P with verified GPIO assignments for
  both SFP ports, LED SET0 (amber 2.5G / green 1G-100M-10M) and SET1
  (SFP all-speeds), led_mux from original firmware register dump, and
  machine_custom_init() enabling LED_GLB_IO_EN bit 6
- doc/devices/FNS-1200P.md: device overview, port layout, serial
  console (S1 three through-holes = UART0 115200 8N1 3.3V),
  LED and SFP GPIO tables
- doc/devices/photos/FNS-1200P/: chassis front panel and PCB top photos
- doc/supported_devices.md: add FNS-1200P to the list

GPIO assignments and LED register values were cross-checked between
live GPIO observation (RTLPlayground gpio command) and an original
firmware register dump.

doc/devices/FNS-1200P.md

@@ -0,0 +1,93 @@
+# FOXNEO FNS-1200P
+
+RTL8372-based 4×2.5G PoE+ + 2×SFP+ unmanaged switch.
+
+Using SPI clamp in-board is the only method for initial installation.
+
+### Label specifications
+
+- **Manufacturer**: FOXNEO
+- **Model**: FNS-1200P
+- **Ports**:
+  - 4 × RJ45: 10/100/1000/2500 Mbps with PoE+
+  - 2 × SFP+: 1G / 2.5G / 10G
+
+### What works
+
+- All four 2.5GBASE-T RJ45 ports at 10/100/1000/2500 Mbps (PoE+ is not configurable via RTLPlayground)
+- Both SFP+ ports supporting 1G, 2.5G and 10G modules
+- LEDs: amber (2.5G) and green (1G/100M/10M) per copper port; combined link/act on SFP ports
+
+### PCB overview
+
+**Board markings**
+- Top silkscreen: PCB-K0402W-U13-V2.0 / DIP-K0402WB-V2.0
+
+**Key components**
+- U3: SPI NOR flash, 2 MiB
+- U7: unpopulated SOP8 footprint — I2C bus (RTL8372 slave at 0x5c) is accessible from its pads, useful for register dumps
+- S1: unpopulated slide switch footprint (three through-holes used as serial console)
+
+Front panel
+
+<img src="photos/FNS-1200P/chassis-front.jpg" width="400" />
+
+Top side (PCB)
+
+<img src="photos/FNS-1200P/PCB-top.jpg" width="300" />
+
+### Port layout
+
+| Front panel position | Logical port | Physical port | Type    |
+|----------------------|--------------|---------------|---------|
+| SFP left             | 8            | 5             | SFP+    |
+| RJ45 1               | 4            | 1             | Copper  |
+| RJ45 2               | 5            | 2             | Copper  |
+| RJ45 3               | 6            | 3             | Copper  |
+| RJ45 4               | 7            | 4             | Copper  |
+| SFP right            | 3            | 6             | SFP+    |
+
+### Serial console
+
+The PCB has three unpopulated through-holes intended for a slide switch, directly connected to UART0.
+Numbered from the left (SFP port side), the pinout is:
+
+| Position (left→right) | Signal | GPIO                     |
+|-----------------------|--------|--------------------------|
+| 1 (leftmost)          | RX     | GPIO32\_UART0\_RX (32)   |
+| 2 (middle)            | GND    | GND                      |
+| 3 (rightmost)         | TX     | GPIO31\_UART0\_TX (31)   |
+
+- **Settings**: 115200 baud / 8N1 / 3.3V TTL
+- Connect a USB-TTL adapter: adapter TX → pin 1, GND → pin 2, adapter RX → pin 3
+
+### LED configuration
+
+Copper ports use LED SET0, SFP ports use LED SET1.
+
+| SET  | LED0                                             | LED2                                              |
+|------|--------------------------------------------------|---------------------------------------------------|
+| SET0 | Amber — lights on 2.5G link                      | Green — lights on 1G / 100M / 10M link            |
+| SET1 | All speeds — lights on any link with activity    | —                                                 |
+
+LED pad to physical port mapping:
+
+| GPIO pads | Port                    |
+|-----------|-------------------------|
+| GPIO8–11  | Physical port 5 (left SFP)  |
+| GPIO12–14 | Physical port 1 (RJ45 1)    |
+| GPIO15–17 | Physical port 2 (RJ45 2)    |
+| GPIO18–20 | Physical port 3 (RJ45 3)    |
+| GPIO21–23 | Physical port 4 (RJ45 4)    |
+| GPIO24–27 | Physical port 6 (right SFP) |
+
+### SFP GPIO assignments
+
+| SFP              | pin\_detect (ModAbs)        | pin\_los               | SerDes | I2C SDA              | I2C SCL                  |
+|------------------|-----------------------------|------------------------|--------|----------------------|--------------------------|
+| Left (logical 8) | GPIO30\_ACL\_BIT3\_EN       | GPIO37                 | SDS1   | GPIO39\_I2C\_SDA4    | GPIO40\_I2C\_SCL3\_MDC1  |
+| Right (logical 3)| GPIO50\_I2C\_SCL2\_UART1\_TX | GPIO51\_I2C\_SDA2\_UART1\_RX | SDS0 | GPIO41\_I2C\_SDA3\_MDIO1 | GPIO40\_I2C\_SCL3\_MDC1 |
+
+GPIO assignments were verified by observing GPIO state changes during SFP module insertion/removal
+and cross-checked against an original firmware register dump.
+`pin_tx_disable` is GPIO\_NA on both ports (original firmware keeps all GPIOs as inputs).

doc/supported_devices.md

@@ -9,6 +9,7 @@ The following devices have been tested and are fully working:
 - No-Name ZX-SWTGW215AS, managed version of kp-9000-6hx-x, ordered on
   AliExpress as keepLINK 5+1 port managed
 - TrendNet TEG-S562 (RTL8372: 4x 2.5GBit + 2x 10GBit SFP+)
+- FNS-1200P (RTL8372: 4x 2.5GBit + 2x 10GBit SFP+)
 
 Other device based on RTL8272/3 that may work are described here: [Up-N-Atoms 2.5 GBit RTL Switch hacking guide]
 (https://github.com/up-n-atom/SWTG118AS)