Add support for SoftwareSerial to the elechouse Arduino NFC library for PN532 (https://github.com/elechouse/PN532). It’s just their PN532_HSU, modified to use SoftwareSerial.

example.cpp

#include <SoftwareSerial.h>
#include <PN532_SWHSU.h>
#include <PN532.h>

SoftwareSerial SWSerial( 10, 11 ); // RX, TX

PN532_SWHSU pn532swhsu( SWSerial );
PN532 nfc( pn532swhsu );

void setup(void)
{
    nfc.begin();

    // and continue with the examples
}

PN532_SWHSU.cpp

#include "PN532_SWHSU.h"
#include "PN532_debug.h"


PN532_SWHSU::PN532_SWHSU(SoftwareSerial &serial)
{
    _serial = &serial;
    command = 0;
}

void PN532_SWHSU::begin()
{
    _serial->begin(115200);
}

void PN532_SWHSU::wakeup()
{
    _serial->write((uint8_t) 0x55);
    _serial->write((uint8_t) 0x55);
    _serial->write((uint8_t) 0);
    _serial->write((uint8_t) 0);
    _serial->write((uint8_t) 0);

    /** dump serial buffer */
    if(_serial->available()){
        DMSG("Dump serial buffer: ");
    }
    while(_serial->available()){
        uint8_t ret = _serial->read();
        DMSG_HEX(ret);
    }

}

int8_t PN532_SWHSU::writeCommand(const uint8_t *header, uint8_t hlen, const uint8_t *body, uint8_t blen)
{

    /** dump serial buffer */
    if(_serial->available()){
        DMSG("Dump serial buffer: ");
    }
    while(_serial->available()){
        uint8_t ret = _serial->read();
        DMSG_HEX(ret);
    }

    command = header[0];
    
    _serial->write((uint8_t) PN532_PREAMBLE);
    _serial->write((uint8_t) PN532_STARTCODE1);
    _serial->write((uint8_t) PN532_STARTCODE2);
    
    uint8_t length = hlen + blen + 1;   // length of data field: TFI + DATA
    _serial->write((uint8_t) length);
    _serial->write((uint8_t) ~length + 1);         // checksum of length
    
    _serial->write((uint8_t) PN532_HOSTTOPN532);
    uint8_t sum = PN532_HOSTTOPN532;    // sum of TFI + DATA

    DMSG("\nWrite: ");
    
    _serial->write(header, hlen);
    for (uint8_t i = 0; i < hlen; i++) {
        sum += header[i];

        DMSG_HEX(header[i]);
    }

    _serial->write(body, blen);
    for (uint8_t i = 0; i < blen; i++) {
        sum += body[i];

        DMSG_HEX(body[i]);
    }
    
    uint8_t checksum = ~sum + 1;            // checksum of TFI + DATA
    _serial->write((uint8_t) checksum);
    _serial->write((uint8_t) PN532_POSTAMBLE);

    return readAckFrame();
}

int16_t PN532_SWHSU::readResponse(uint8_t buf[], uint8_t len, uint16_t timeout)
{
    uint8_t tmp[3];
    
    DMSG("\nRead:  ");
    
    /** Frame Preamble and Start Code */
    if(receive(tmp, 3, timeout)<=0){
        return PN532_TIMEOUT;
    }
    if(0 != tmp[0] || 0!= tmp[1] || 0xFF != tmp[2]){
        DMSG("Preamble error");
        return PN532_INVALID_FRAME;
    }
    
    /** receive length and check */
    uint8_t length[2];
    if(receive(length, 2, timeout) <= 0){
        return PN532_TIMEOUT;
    }
    if( 0 != (uint8_t)(length[0] + length[1]) ){
        DMSG("Length error");
        return PN532_INVALID_FRAME;
    }
    length[0] -= 2;
    if( length[0] > len){
        return PN532_NO_SPACE;
    }
    
    /** receive command byte */
    uint8_t cmd = command + 1;               // response command
    if(receive(tmp, 2, timeout) <= 0){
        return PN532_TIMEOUT;
    }
    if( PN532_PN532TOHOST != tmp[0] || cmd != tmp[1]){
        DMSG("Command error");
        return PN532_INVALID_FRAME;
    }
    
    if(receive(buf, length[0], timeout) != length[0]){
        return PN532_TIMEOUT;
    }
    uint8_t sum = PN532_PN532TOHOST + cmd;
    for(uint8_t i=0; i<length[0]; i++){
        sum += buf[i];
    }
    
    /** checksum and postamble */
    if(receive(tmp, 2, timeout) <= 0){
        return PN532_TIMEOUT;
    }
    if( 0 != (uint8_t)(sum + tmp[0]) || 0 != tmp[1] ){
        DMSG("Checksum error");
        return PN532_INVALID_FRAME;
    }
    
    return length[0];
}

int8_t PN532_SWHSU::readAckFrame()
{
    const uint8_t PN532_ACK[] = {0, 0, 0xFF, 0, 0xFF, 0};
    uint8_t ackBuf[sizeof(PN532_ACK)];
    
    DMSG("\nAck: ");
    
    if( receive(ackBuf, sizeof(PN532_ACK), PN532_ACK_WAIT_TIME) <= 0 ){
        DMSG("Timeout\n");
        return PN532_TIMEOUT;
    }
    
    if( memcmp(ackBuf, PN532_ACK, sizeof(PN532_ACK)) ){
        DMSG("Invalid\n");
        return PN532_INVALID_ACK;
    }
    return 0;
}

/**
    @brief receive data .
    @param buf --> return value buffer.
           len --> length expect to receive.
           timeout --> time of reveiving
    @retval number of received bytes, 0 means no data received.
*/
int8_t PN532_SWHSU::receive(uint8_t *buf, int len, uint16_t timeout)
{
  int read_bytes = 0;
  int ret;
  unsigned long start_millis;
  
  while (read_bytes < len) {
    start_millis = millis();
    do {
      ret = _serial->read();
      if (ret >= 0) {
        break;
     }
    } while((timeout == 0) || ((millis()- start_millis ) < timeout));
    
    if (ret < 0) {
        if(read_bytes){
            return read_bytes;
        }else{
            return PN532_TIMEOUT;
        }
    }
    buf[read_bytes] = (uint8_t)ret;
    DMSG_HEX(ret);
    read_bytes++;
  }
  return read_bytes;
}

PN532_SWHSU.h

#ifndef __PN532_SWHSU_H__
#define __PN532_SWHSU_H__

#include <SoftwareSerial.h>

#include "PN532Interface.h"
#include "Arduino.h"

#define PN532_SWHSU_DEBUG

#define PN532_SWHSU_READ_TIMEOUT						(1000)

class PN532_SWHSU : public PN532Interface {
public:
    PN532_SWHSU(SoftwareSerial &serial);
    
    void begin();
    void wakeup();
    virtual int8_t writeCommand(const uint8_t *header, uint8_t hlen, const uint8_t *body = 0, uint8_t blen = 0);
    int16_t readResponse(uint8_t buf[], uint8_t len, uint16_t timeout);
    
private:
    SoftwareSerial* _serial;
    uint8_t command;
    
    int8_t readAckFrame();
    
    int8_t receive(uint8_t *buf, int len, uint16_t timeout=PN532_SWHSU_READ_TIMEOUT);
};

#endif