Introduce all alternative pins per peripheral

- Alternate pins (PY_n_ALTx)
- Dual pad pins (PY_n_C)
- Remap pins (PY_n_R)

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/PinNames.h

@@ -8,6 +8,25 @@
 extern "C" {
 #endif
 
+// Alternative possibilities which use other HW peripheral instances
+#define ALT0        0x100
+#define ALT1        0x200
+#define ALT2        0x300
+#define ALT3        0x400
+#define ALT4        0x500
+#define ALT5        0x600
+#define ALT6        0x700
+
+// Specific pins
+// Dual pad pin
+// Direct channels are connected to analog I/Os
+// (PY_C) to optimize ADC performance.
+#define PDUAL       0x2000
+// Remap pin
+#define PREMAP      0x3000
+// PinName mask
+#define PNAME_MASK  0xFF
+
 typedef enum {
   // Not connected
   NC = (int)0xFFFFFFFF,

keywords.txt

@@ -726,6 +726,16 @@ PADC_TEMP	LITERAL1
 PADC_VREF	LITERAL1
 PADC_VBAT	LITERAL1
 
+ALT0	LITERAL1
+ALT1	LITERAL1
+ALT2	LITERAL1
+ALT3	LITERAL1
+ALT4	LITERAL1
+ALT5	LITERAL1
+ALT6	LITERAL1
+PDUAL	LITERAL1
+PREMAP	LITERAL1
+
 # Port Name
 PortName	KEYWORD3
 FirstPort